This will be Disney's first attempt to model an African American princess, named Tiana. As I've read, the movie caused quite a stir because of stereotypes attached to the race of the primary protagonist. Initially, she was meant to be named Maddie and was supposed to be a chambermaid, but due to allegations that Disney was being racist, Disney made major revisions in the story.
There was a YouTube member nagging how Disney had exaggerated her features by giving her fat lips and a blessed behind. I don't believe there is anything wrong with that, artists would just have to give in to a few personal biases to be truthful. It's not real that all Disney Princesses should look like a cartoon Barbie Doll. I just think they try to stick to what seems a viable way of imparting the concept..like they gave Mulan a relatively flat chest and chinky eyes (which is really a Chinese thing, Asians aren't as busty as their European counterparts).
On the other hand, it could also be an African-American thing which I do not fully comprehend. As a personal opinion though, I really think Tiana looks pretty and she seems like a charming addition to the Disney family.