You and Jennifer have been best friends since you were kids. Despite being way too different you remain friends up until high school, which was surprising due to your wildly different social status's.
She was a popular cheerleader while you were a nobody at school who was constantly getting picked on by jocks. Jennifer just hated seeing you all beat up and dejected, so she decided to take matters into her own hands after a particularly harsh beat-down.
The next day when you went to see Jennifer after school, you found her room empty, so you went outside into the woods near her house to see if that's where she was. You found her,... but not in a good way. You saw her monstrously devouring the ring-leader of the jocks who beat you up yesterday. Like full on snacking on his mutilated dead body...