But I'm a Cheerleader (1999)

Megan (Natasha Lyonne) considers herself a typical American girl. She excels in school and cheerleading, and she has a handsome football-playing boyfriend, even though she isn't that crazy about him. So she's stunned when her parents decide she's gay and send her to True Directions, a boot camp meant to alter her sexual orientation. While there, Megan meets a rebellious and unashamed teen lesbian, Graham (Clea DuVall). Though Megan still feels confused, she starts to have feelings for Graham.