Plot hole: When Charlotte kissed Naveen at the end, she should've turned into a frog as well because she was no longer a princess.
Suggested correction: When ordinary people kiss a frog, they don't transform into anything. (Perhaps they die from infection after a few days.) Charlotte was just an ordinary person. Tiana was chosen. She wished upon the star. Naveen and the consequences of kissing Naveen were a result of Tiana's wish.
Suggested correction: How? She was no longer a princess.
Tiana turned into a frog because she kissed Naveen without being a princess, so Charlotte should have, too.
Tiana broke the talisman that the voodoo man had, thus breaking any more frog-turning spell. I know Mama Odie said that Naveen and Tiana broke the spell when they got married, but Dr. Facilier was still responsible for the spell in the first place, and he died, so there's that.