15. Bella Thorne – 18
The Disney Channel star has started focusing on her music career and transitioning to a more adult career. To that end, she has started wearing a more mature wardrobe and turning an older edge to her modeling and her music. So it may come as a surprise that she is really only 18 years old. She has plenty of time to keep rocking the young look before she really needs to start acting more like a full-blown adult.