"I try to do different things all the time. I try not to rely on trends. I think you just kind of work with what works for you," the star, who just turned 18 last month, told Us at Cosmopolitan's Fun Fearless Awards in NYC March 5.
"My mom probably has told me that less is more and that you never want to look like you're trying too hard to be something that you may actually not be -- something that's not you," she continued.
It's exactly that mature but casual outlook that has landed Fanning, who was one of the evening's honorees, the spokesmodel gig for Marc Jacobs' Oh Lola! fragrance in 2010.
The starlet, who broke out in the 2001 film I Am Sam, has taken quite a few fashion risks over the years -- something that her younger sister Elle Fanning, 13, has clearly inherited.
"I think [my style has] evolved because I started doing this kind of thing when I was six, so I obviously couldn't wear something like this when I was six!" she laughed, referring to her ice blue Miu Miu dress with a deep, v-neck and cutout along the waist.