Forgive me if this was already stated (too many posts to wade through), but IMO the issue is her hair. Tiana rocks a low pony through most of the movie, then at the end is rocking a high pony in her flapper dress. The short hair just isn't as "youthful" of a hair style, and also happens to match Eudora's in the film, therefore the "looks like her mom" comparisons.
They changed Arial's hair in her ride, so maybe they will do the same here after guest feedback. Seems like an easy fix to make her feel more like Tiana.