Responses
I think her mom was a witch or dark sorcereress...
Or just a magic user in general and her daughter inherited that but it became twitches as her anger/jealousy grew
beta
Options:
1. Born evil - pretended to be a harmless
2. Something demonic entered her before entering the palace
a. like the case of the one villainess who was originally human but due to dark magic, was born as a human but with a demon soul
3. Her desire for better treatment invited something evil in her after entering the palace (invite as in attracted the entity)
4. Her desire for better treatment led her to become evil and invited dark practices + evil (she made a way to invite the evilness herself)
(⊙…⊙ )