Mary Elizabeth is a character in Perks Of Being Wallflower, as well as Charlie's first girlfriend.
In the film, she is portrayed by Mae Whitman.
Mary Elizabeth, though a funny, sweet girl, relies on her popularity and cares what people say and think of her. She is very self-determined.
Mary Elizabeth shortly dates Charlie but it does not work out. Charlie used to listen to her and hear what she had to say. At the end of the book, she tells Charlie that now she was dating a guy she was really meant to be with. She argued all the time with her new boyfriend about social issues, and Charlie really didn't like Mary that much.
Mary Elizabeth breaks up with Charlie after a game of truth or dare where Charlie was asked to kiss the prettiest girl in the room. Instead of kissing Mary Elizabeth like everyone expected him to, he kissed Sam which caused Mary Elizabeth great sadness.
She briefly dated Charlie, but Charlie becomes frustrated with their relationship because he believes she doesn't seem to care about what his's opinions are and she just keeps talking and talking. The two break up when Sam, Patrick, Charlie and herself are playing truth or dare. Patrick dares Charlie to kiss the prettiest girl in the room and he kisses Sam instead of her. She and the rest of their group isolates themselves from him, but they later make up.