Ella enchanted, Yes Man, Yes, several others I'm sure.
Magic exists, a girl crosses the path of a gypsy, receives the curse of 'yes'.
Things start slow, she might not even notice it is happening, but eventually someone says something she has no desire to agree with, and does anyway. She starts to realize the curse and tries to find loopholes to get out of embarrassing herself. But, the more she tries to make a yes look like a no, the more attention she attracts from those in school that believe in things like curses.
Open for discussion.
Closed for now.