Mandy Moore, the 19-year-old film ingenue, has just finished a whirlwind summer: shooting in Venice, prepping for the release of her next CD, Coverage, not to mention sideline cheering for her tennis-star boyfriend, Andy Roddick. Believe it or not, the once-blonde pop princess and former tomboy (with not-so-distant memories of the Florida Mall in Orlando) didn’t consider herself particularly fashion-savvy, let alone fashion-obsessed, until recently. She spent last year in a Catholic-school uniform for the Michael Stipe–produced Saved, due out this fall. But for the untitled project she just wrapped, in which she plays the president’s daughter, she donned a Gucci motorcycle jacket and a pale-pink Chloé pantsuit, awakening her inner clotheshorse. “Today I bought a tweed fedora from Prada,” she says. “I have the little white Louis Vuitton bag with all the colored LVs, and even my dad was like, ‘That’s one of the coolest purses I’ve ever seen!’ ”