Charlie’s sister is a senior in high school, although she doesn’t run in the same social group as Patrick and Sam. Instead, she seems to be more traditionally popular and always has a boyfriend. However, despite the fact that Charlie’s sister and Sam aren’t friends, their character arcs run parallel to each other in many ways, especially when it comes to their unhealthy relationships with men. While Charlie’s sister doesn’t have the history of childhood sexual abuse that Sam does, she still exists in a world that dehumanizes and sexually objectifies women, and she finds herself in an abusive relationship that takes almost the entire novel for her to escape. At the beginning of The Perks of Being A Wallflower, Charlie’s sister is still working through her own thoughts and understanding of gender roles. While her critical reaction to Mary Bailey’s character in It’s a Wonderful Life suggests that she wants to shirk traditional expectations of womanhood, she still pushes her boyfriend to be more assertive and traditionally masculine by mocking him for failing to stand up to his bullies in prior years. When her boyfriend responds by hitting her in the face, Charlie’s sister becomes submissive and kind, seeking to continue the relationship despite the physical violence.

Her confusion about gender dynamics grows when Charlie’s brother brags about his new girlfriend, who’s confident and smart, mentioning that she would never allow a man to hit her and would break up with him if he did. Charlie’s sister is angered by this comment and starts an argument – it’s understandably difficult for her, an intelligent, hard-working woman herself, to reconcile the fact that she has become the sort of constrained, docile woman she used to scoff at. Charlie’s sister faces cognitive dissonance when comparing her perception of herself as a strong woman to her reality of being the victim in an abusive relationship. When Charlie’s sister tells him about Sam’s reputation at school and suggests that Sam’s unhealthy relationships with men come from a lack of self-esteem, her comment is just as much a projection of her own self-esteem issues as it is an accurate appraisal of Sam. Charlie’s sister can understand how other women end up in abusive or unloving relationships, but she can’t yet admit to herself that she is in the same boat.

Charlie’s relationship with his sister is one common among siblings – sometimes she’s snappish, sometimes she’s nice – but their bond deepens throughout the novel as they both learn to open up to each other and lean on one another for support. When Charlie’s sister’s toxic boyfriend coldly breaks up with her and refuses to support her when she confesses to him that she’s pregnant, she turns to Charlie for support. He accompanies her to her abortion and keeps the situation hidden from their parents, and his discretion means a lot to his sister. While they live very different lives in and out of school, they can both rely on each other for love and support. And, like Sam, by the end of the novel, Charlie’s sister has moved on from her abuser and seems to be headed down a healthier path with her next romantic relationship.