"She is young and sweet and beautiful," Marc Jacobs has said. "The epitome of this girl I fantasize of." No prizes for guessing that the designer was talking about Sofia Coppola, the friend and muse who appeared naked—all bee-stung lips and imperfect, crooked nose—in an ad for his signature fragrance, Blush. This fall, the girl who professes indifference to the publicity machine will again be exposed to the spotlight's glare as she releases her stylized biopic, Marie Antoinette. Like her previous movies, The Virgin Suicides and the Oscar-winning Lost in Translation, it's a coming-of-age story—one that was filmed at Versailles, stars American actors, and features a soundtrack by Bow Wow Wow and New Order. Critics at Cannes were divided, but judging from the recent Dior and Chanel couture collections, the film's fashion influence has already been felt.

On set, Coppola sports a tomboy's jeans and designer sweaters; off, she wears girlish clothes that perfectly suit her gamine-like frame—baby-doll dresses, ballerina flats, and when the Academy calls, a Marc Jacobs column gown. But there's no doubt that this famous Hollywood offspring, and regular on Vogue's Best-Dressed List, is all grown up. Following the release of her film this fall, Coppola will add another title to her resume: mother. She's expecting her first baby, with Thomas Mars of the French indie-rock band, Phoenix, in November.

—Sarah Cristobal