* The hero: Tiana, a young woman who is transformed into a frog.
* The villain: Mama Odie, a voodoo priestess, turns the villainous Prince Naveen into a frog, but he is not the main antagonist. The main antagonist is Dr. Facilier, a shadowy voodoo practitioner who uses magic to control the prince and ultimately tries to take over New Orleans.
While the movie doesn't feature a snake woman, it does have a compelling villain and a complex story with strong themes. If you're thinking of another movie, please let me know!