Sienna Miller; W Jan 07

Sienna Miller has unfastened the safety pin holding her short Zara skirt closed and is squeezing the tummy fat around her belly button into the shape of a bagel. "Press it," she says, giggling goofily. "You can really squish it in!"

It must be said that, for a girl hired to play the role of a bulimic and drugged-out Edie Sedgwick, Miller can gather an impressive amount of dough. Then again, the temporary tubbiness might have something to do with the Magnolia Bakery cupcakes and bottle of Pinot Grigio that we've been sharing. Although Miller's publicist has insisted that this interview last only an hour and take place over tea in the cordoned-off bar at the Gramercy Park Hotel, things have taken a slightly different turn. Soon after meeting and deciding that the tea would have to wait until the morning, Miller suggests that we head upstairs to her suite to listen to original recorded conversations between Andy Warhol and Sedgwick. Clearly, she's not the type to worry about protocol. "They're going to kill me for having invited you up here," says the actress, lighting a cigarette and resting her feet on my chair. "But I'd rather have someone judge me honestly than try to create some sort of image."

Starting in late December, the whole world will be judging Miller, honestly or not. In the much buzzed-about film Factory Girl, directed by George Hickenlooper (Mayor of the Sunset Strip), she has her first major leading role, as Sedgwick, Warhol's tragic muse during the heyday of the Factory. Even before its release, Factory Girl has attracted plenty of bad press, including reports of last-minute shoots to fill holes in the storyline. Indeed, after this interview, Miller and Guy Pearce, who plays Warhol, will drive up to the Connecticut home of Harvey Weinstein, whose company is releasing the film, for a late-night strategy session, to be followed by a week of intense shooting. But despite its alleged problems (the movie wasn't ready to be screened at press time), Factory Girl is set for release a month earlier than originally planned, in order to be considered for the Academy Awards. The reason, insiders say, is that Miller's scene-stealing portrayal of Sedgwick has her in line to be a legitimate Oscar contender. (Weinstein took out "For Your Consideration" ads for Miller in the trade press even before the film was finished.) Either way, the movie will catapult the 25-year-old from being known primarily as the fashionable girlfriend of Jude Law, whom she's dated on and off since 2003, to an actress with serious star potential.

Miller bears such a strong physical resemblance to Sedgwick that it would seem to be a role she was born to play. In fact, Factory Girl producer Holly Wiersma decided she wanted Miller for the part after noticing her in a fashion layout in this magazine two years ago. "I saw a photo of her in a tub with a bottle of champagne and thought, That's Edie," says Wiersma, who immediately flew to London to meet the actress. Miller auditioned and snagged the part on the spot—but holding on to it wasn't so easy. Though the film was scheduled to start production in early 2005, there were problems with financing, and in May of that year Miller, anxious to work, accepted an offer to play Celia in a West End production of As You Like It. Katie Holmes was subsequently cast as Sedgwick, before the role went back to Miller once the play ended. (The tabloids ran with the explanation that Holmes's new boyfriend, Tom Cruise, persuaded her to drop out of the potentially risqué film. Of this, Miller says, "I'm not really sure of the ins and outs.")

What had begun as the most exciting year in Miller's career devolved into one of her most traumatic when, in July 2005, Jude Law publicly admitted to cheating on Miller with his children's nanny. The affair sparked a tabloid frenzy that only intensified a few months later, when the actress decided to take Law back. "There were times when I felt like it was all just too much to deal with," she recalls, declining to share the details. (Miller admits that she's tried therapy, but after angrily calling the therapist a "cow" in response to a particularly difficult question in the first session, she was told she was still in trauma and not ready for analysis. She has not been back since.) The media, Miller adds, "is just a bigger animal than I will ever be. It just becomes this soap opera. And I guess I had a pretty good few episodes."

Today, Miller is unsure about how she wants to publicly define her relationship with Law. While her engagement ring is long gone, she's wearing an Irish Claddagh ring on her middle finger, with diamonds in the center heart. It was a gift from Law. If a woman wears the heart facing inward, it is said to mean that her heart is taken. If facing the other way, her heart is still open. When it's pointed out that Miller has the heart facing in, she takes it off and holds it sideways against her finger. "What does it mean if it's like this?" she says, jokingly, before explaining further. "I'm wearing it because it's a beautiful ring, and he's a very close person in my life."

Although Miller is well aware that dating Law, whom she met on the set of Alfie, has overshadowed her somewhat limited film career (Casanova, Layer Cake), she says she has no regrets about their involvement. And while it's obvious that being with the actor has elevated her public profile, she insists that wasn't her plan. "I was just never desperate to be famous, which I know sounds clichéd and probably like a lie, but it is, in my case, very true," she says. "And that's the irony of my situation. It was always about acting, and now it's all about everything but that. I fell in love with someone very, very famous, and that's beyond all of our control. Strategically I probably could have analyzed it at the time and thought, This could potentially be very damaging, but that was a very beautiful period of my life."

With Factory Girl, Miller hopes that people will finally be able to see her as an actress and not just as one half of a celebrity couple. "I know that I have a lot to prove to a certain degree, but it's fine," she says with a shrug. In preparing for the role, Miller, who claims to be a voracious reader, spent months poring over books about the Warhol era and biographies of Sedgwick, studying not just Edie's brief reign as the toast of downtown New York but also her isolated childhood in Santa Barbara, California, and her depraved post-Andy fall from grace, culminating in her 1971 fatal barbiturate overdose. Likening herself to a detective, Miller says she particularly loved delving into that moment in history, studying not just the cast of characters during the Factory days but also the political and sociological climate of the mid-Sixties. Miller also spent time with some of the key people in Sedgwick's life, including Brigid Berlin, who generously gave Miller a handful of crystals that Warhol carried around with him during his last days, as well as Michael Post, who was married to Sedgwick when she passed away. In addition, Miller studied Sedgwick's voice with recordings on loan from the Andy Warhol Museum in Pittsburgh. Because she had such a distinct speech pattern—"It's almost English," says Miller. "There's nothing nasal or twangy; it's sort of old-fashioned, upper-class American"—the actress felt it was essential to get it right. (Judging from the recordings, she succeeded.)

While Miller dismisses any facile comparisons between her own personal qualities and Edie's self-destructive character—"She just walked this fine line of extinction. And it's sort of fascinating, because that's not who I am. But I empathize with her"—her director and costars found the similarities impossible to ignore.

"I think it's startling how accurate Sienna is," says Hickenlooper, who has directed several leading ladies at the start of their careers, including Naomi Watts and Renée Zellweger, and considers Miller far and away the most talented. "She evokes the same kind of emotional response that I imagine Edie did. She's got so much charisma and effervescence. When you meet her, it's like being hit by a strong wind."

"Sienna is kind of naturally Edie," adds Pearce. "She's got a bit of a mad quality about her, though I'd assume that she's much more stable than Edie. She can be distracted easily—which is not a bad thing. She's got a lot going on in her head, and she has a great amount of energy and emotion. It makes her performance unpredictable and lively."

Adds Weinstein in an e-mail, "Sienna's performance is unbelievably convincing and definitely has awards potential. Her sophistication and style are irresistible and rarely seen onscreen."

Physically, the role demanded one significant transformation: Miller had to get down to a size zero. Bagel belly notwithstanding, she is already skinny by most people's standards, but Sedgwick bordered on gaunt, thanks to a trifecta of drugs, depression and an eating disorder. Miller credits Hickenlooper with helping her slim down. "I'd order an omelet and he'd make it an egg-white omelet," she says, laughing. "I thought, Okay, I'll drink vodka instead of wine because it has less calories. George would come along and actually snatch bagels out of my hand!"

Since Factory Girl wrapped, in early 2006, Miller has been diligently building her repertoire. She's shot four films, most of them small indies, including Interview, a drama in which she plays a soap-opera star opposite Steve Buscemi, and the dark comedy Camille, in which she's an unlucky-in-love newlywed on her honeymoon, with James Franco as her husband. But it's the Edie character that has been hardest for her to shake. "I was left feeling a little bit lost afterwards," she says. "You work so intently on something, and then suddenly it's over. What do you do with the information? What do you do with the way that you were smoking at that time, the way she smoked? You're suddenly left with all these mannerisms that you've perfected. It's weird. I forgot how to dance like I used to dance."

At the moment, Miller is far from sure about what the future holds. Beyond spending Christmas with her mother and a close girlfriend in Africa, she has few definite plans. On a lark, she's launching a women's fashion collection, called twenty8twelve (a reference to her birthday, December 28), with her older sister, Savannah, a designer who formerly worked for Alexander McQueen. She describes the line, slated to debut in the fall, as part Patti Smith and part "back alley Jack the Ripper," with items like long masculine coats that sweep the floor. London stores such as Harvey Nichols and Browns have already expressed interest, but Miller insists she has no entrepreneurial aspirations to capitalize on her celebritydom in order to build a megamillion-dollar business. "It doesn't matter if it fails or if it doesn't," she says. "It just seemed like a fun thing to do," primarily because it allowed her to work with her sister, with whom she is extremely close. (Miller's British mother, a former model, and American father, an investment banker, are divorced. Although she was born in New York, she moved to London when she was one year old and, at the age of eight, was enrolled at Heathfield, a posh boarding school in Ascot.)

Come January, she will be moving into the first home that she's purchased with her own money. It's a three-story "old spitfire bomber building" in London that she plans on decorating herself in "decaying grandeur" style with antiques found at local markets. Of late, Miller says, she's been forced to neglect her family and friends in favor of her work, and she has already dreamed up a very specific fantasy of a perfect day in her new house. "On Sunday, I'll get up at 11, get the Times, have my tea and feed my dogs, put a chicken in the oven," she begins. "Then all my friends will come over, and we'll sit around and watch football and eat roast chicken with potatoes. Then we'll have leftovers at 8." Miller stares off wistfully, before adding, "God, I sound like some bohemian lovey. I'm actually pretty rock 'n' roll as well!"

One thing Miller certainly isn't is a typical Hollywood starlet. Despite her history of paparazzi run-ins, she prefers to do without personal security guards. The same goes for an assistant. "I just think the more you live your life like that, the more attention you attract," she says. The vast gulf between Miller and her American counterparts becomes particularly apparent during her extended stints in Los Angeles, where Miller, who has no driver's license, says her existence has sometimes been lonely. And forget about Hollywood nightlife—she insists that she's been to only one L.A. nightclub, once, for 30 minutes: "I can't sit and pose with a glass of champagne, especially at those places where you know there's going to be a photographer, and all those girls are posing with each other, looking like they're best friends, when they've just met."

Miller finds it ironic that she's perceived as a party girl, since she claims to go out less than other young actresses; to hear her tell it, she's just the one who gets caught. It's been the case ever since her boarding-school days, when all the girls would smoke but the headmaster would inevitably catch her in the act. (Her family nickname is Gizmo, after the devilish gremlin.) Miller does, however, live up to her reputation tonight, when, after her meeting with Weinstein, and well past midnight, she heads to Bungalow 8. Unlike Sedgwick, whose excessive partying went hand in hand with mental instability, the actress says she just likes to have a good time. Socializing over alcohol is simply how she was raised. "I was brought up in a culture where, when you're 12 years old, you're given a glass of wine at dinner—it was never a novelty," she explains. Of a childhood spent at the constant side of her less-than-conservative parents, even at cocktail parties, she says, "I grew up being put to sleep upstairs in a spare room, and you're sort of half awake and you can hear the laughing and smell cigarettes and booze, and then they carry you home and you pretend to be asleep. You can smell wine and cigarettes on their breath. That's like mother's milk to me."

Of course, it's also easy to capture the attention of the paparazzi when wearing high-fashion getups worthy of a runway show. Her wardrobe, in fact, landed her in the fashion magazines way before anyone could name any of her films. Miller, who still doesn't employ a stylist, says she is perfectly capable of shopping for her own clothes, though she does have a closetful of freebies. Today she's dressed in basic black, accessorized with knee-high gold python Devi Kroell boots and a bondage harness from Coco de Mer strapped across her chest. Much has been written about how Miller became a model before taking up acting, which she says is a hilarious overstatement: "I'm five foot six! I did Abercrombie & Fitch and the Pirelli calendar, but I wasn't doing high fashion," she insists. "I was the little one with the personality who got booked because everyone thought I'd make them laugh on set."

That strong personality has also landed her in a bit of trouble as of late. Recently the tabloids ran a story about the actress throwing a temper tantrum outside of a Pittsburgh bar after she was denied entry for not having an ID. Miller says it never happened. "I don't feel any more important than anyone else because of what I'm doing," she explains. "That's why it really riles me when I hear these stories about me screaming that I'm famous. It's absolutely not my perception of myself or the way I live my life."

It's after 7 p.m. now, and Miller, who has been talking candidly about herself for three hours, seems to be growing bored of the subject. She stubs out a cigarette, downs the last drop of her wine, throws on one of her trademark fedora hats and heads down to the lobby to meet Pearce. The two haven't seen each other in almost a year. When she finds him, she jumps into his arms and wraps her legs around his waist, wildly kissing him on the cheek. From afar, she looks just like Edie.