Sienna Miller, the undisputed It girl of the moment, was radiant at the Ziegfeld Theater premiere of Factory Girl, in which she offers an utterly convincing portrayal of Edie Sedgwick, Andy Warhol's hard-partying muse.

Miller's similarities to the late Edie are striking: She's a beautiful blonde media darling who's captivating on film and is a staple of the all-night glam party scene. But unlike Edie, Sienna has her act together-both on and off camera. "This destructive side of Edie can't happen to me because I have a good background," says Sienna. "My parents, whom I love, are very grounded. They've given me a good life."

Miller's parents were in attendance, as was Edie's brother John Sedgwick. Although Edie's father Francis was depicted in the movie as having molested his young daughter (he passed away in 1967), John calls this "an absurdity" and says that it was all part of Edie's media-manipulation tactics. Also on the scene: Edie's best friend, Danny Fields, and a bevy of other Warhol superstars who joined the cast for an after-party at the restaurant below the Hotel Chelsea-former playground to Warhol himself.

The premiere drew an impressive crowd, including Sienna's rumored new squeeze Sean "Diddy" Combs, Jimmy Fallon (who's terrific as Edie's confidant in the film) with girlfriend Nancy Juvonen, Russell Simmons, Damon Dash, Peter Berg, Donna Karan, Armin Amiri, Cynthia Rowley, Anne Dexter Jones, Padma Lakshmi, Mena Suvari, Meredith Ostrom, and Taryn Rose. There was, however, one notable no-show: co-star Hayden Christensen. Hayden's portrayal of a folk rocker modeled after Bob Dylan, and the intimate scene in the movie between the two actors, left tongues wagging. Some speculated that the two actually coupled on camera, but Miller's publicist assured that "she's just a really good actress."