Elle Fanning: Hollywood's New Princess

Physically speaking, Elle Fanning stopped being Dakota Fanning's "little" sister a year and a half ago, when she shot past her now-seventeen-year-old sibling in height. Professionally speaking, the thespian—who began her career at age two playing a younger Dakota in I Am Sam—came into her own after critically acclaimed roles in Sofia Coppola's Somewhere and the summer blockbuster Super 8. (Neither she nor her sister has ever taken an acting class—how's that for natural talent?) But it's Elle's sartorial growth spurt that causes her to squeal with delight.

"I remember the first time Dakota asked me for fashion advice about what to put with what," she says. "I was like, My big sister is asking me?"

It's impossible not to be charmed by Elle Fanning. She's poised, down-to-earth, full of energy and life—and one of the sunniest people you'll ever meet. She is also one of the best dressed. "Is it weird that I'm obsessed with a thirteen-year-old?" Alexa Chung once asked me. Among Elle's fashion admirers are Marc Jacobs (she starred in his fall Marc by Marc Jacobs campaign), Karl Lagerfeld (who hosted Elle, her father, and her grandma in Paris last summer for her very first fashion show, Chanel couture, bien sur), and Rodarte (with whom she's collaborated on a short film and whose dreamy clothes she wears to both school and bar mitzvahs as well as on the red carpet).

"She's the go-to fashion person in the family," Dakota readily admits. "Elle knows every single model, every single collection, every single piece from every single collection. She has a real passion, and it's not at all in a materialistic way. She genuinely appreciates the workmanship and creativity. It's funny, 'cause when you're an older sister, you try to be the leader and example, and I've recently had to accept that we're equals. The day has come when I actually need her help. I've had to admit that to myself and break down and be like, 'Little sister, does this look good?'"

"You should see my computer at home," Elle says. In lieu of Facebook and Twitter—she may be the only teenager who's on neither—she scours style.com and street-style blogs, dragging her favorite looks into desktop folders. "Even before there's a premiere, I'll know my favorite dress from one of the collections," she says. Her usual picks include Valentino and Rodarte, but she's also very excited about Louis Vuitton's spring collection. "Oh my gosh!" she shrieks. "They looked like little cupcakes and pastel pastries—so pretty!"

Unlike the majority of her classmates, who hike up their uniform skirts and wear "lots of makeup," Elle is not a fan of looking too adult. She prefers her uniform below the knees "to change it up," and she never wears lack—"well, almost never," she says. "I'd much rather look like a two-year-old than a 21-year-old." She's obsessed with Marni shoes—"the clunky ones," she explains, "because I feel like I'm too young to wear a super stiletto." Other things she deems off-limits until she's older are diamond jewels, red lipstick, and gowns. "You don't want to do everything right now," she says. "You want to wait for that special moment."

When she and Dakota attended the Met Gala last May (a first for both), Dakota wore a princess-style gown; Elle, a high-neck minidress. "I'm always quirkier!" she says. "If people say something is sort of weird, I'm like, Oh, that's a great compliment!" Consider yourself warned, Us Weekly.

So far, though, the only trouble Elle's gotten into with the tabloids is with her sister. "She steals my clothes!" Dakota protests when asked what she and Elle fight about the most. (For the record, Dakota insists they get along "really well, but I can't say we get along 100 percent of the time because we are real sisters.") "As far as I'm concerned," Dakota continues, "there's a no-closet-sharing policy, but as far as Elle is concerned. . .I'll go in my room, and there will be clothes on the floor, clothes missing, clothes that are now in her closet. Last summer," she says, "I was in London working on a film, and I was looking online and these pictures came up on my homepage. She was in my hat, my dress, my shoes. I called her up and was like, 'I caught you! They photographed you wearing all my stuff. Put it back!'" she shrills.

Yes, Elle is a talented actress, budding fashion icon, and all-around sweetheart, but she's not completely above acting her own age. Her response when Dakota confronted her? "She hung up on me!" Dakota says, laughing. "She didn't care at all."