I think she looks her age. Even Ariana and Selena, I think they look their age since last year. It give the impression they look younger because they're small. I mean, I'm at the same age range and I don't look older than them nor do my friends unless having a cake face. Many people just really start to show aging past their thirties.
Looking young for your age is good though! I used to hate it but now I'm thankful for it because I know I'll appreciate it when I'm a lot older. For now, I'm almost 21 looking 18.