The femcel protagonist has two main bullies -- Chad on the one hand, and her female friend on the other (the only friend she has, a remnant from childhood). Chad overtly bullies her and represents a physical threat to her. Whereas her female friend passive-aggressively bullies her and represents an emotional threat to her.
Chad's bullying, while overt in nature (featuring things like tripping her), has a covert sexual aspect to it. Her friend's bullying, on the other hand, while covert in nature (featuring things like not helping her when she's down), has an overt sexual aspect to it.
What's happening is that her friend is dating Brad, and subtly bullying the femcel protagonist is a sexual strategy to keep her down and ensure that she doesn't become a threat to this relationship.
Chad, on the other hand, is embracing his evolutionary role as an alpha predator, seeking to explicitly brutalize a girl who he considers so low on the social hierarchy that she is only worth being war-raped.
This explicit and implicit bullying comes to a head at the Senior Prom, where the femcel protagonist humiliates herself in the course of mate competition with her friend over Brad, and Chad swoops in to maximize her embarrassment.
The femcel is totally destroyed upon arriving back home, and morphs into her psychopathic alter-ego.
She acts with pure Machiavellian intent now, and first encounters Chad the next day at school. What she does is sexually tease Chad(!), licking him on the ear and whispering to him about how she knows that he gets an erection whenever he sees her. This enticement culminates in her luring him into the locker-room shower stall after school, where she disables his knee with a hockey stick and is shown to domineer over him, before the scene ends. It stands to reason that she has dominatrix sex with him in the interim, as a common female fantasy is sexually dominating a man who's bullied/raped you (JFL), and the movie has an ironic scene where the adage that "nice guy = unfuckable" is juxtaposed with the erotic threat of Chad.
After this, she hangs out with her female friend in an isolated space, where she causes her to have an "accident" and get killed. She fakes emotion in order to report the death to the police, and ingratiate herself with Brad at the funeral, but soon after this seduces Brad, has sex with him, and becomes his new girlfriend.
But several days later she ends up killing Brad, after he becomes suspicious of her avoidance of the police, probably over Chad's rape and assault allegations, since her cover-story for her friend's death was sound.
Meantime she has manipulated her parents into a divorce, and it should be noted that the father is literally a cosmetic surgeon! He is obsessed with looks, and after killing Brad, she goes to his house, strips naked in front of him, and asks whether she's pretty and whether he'd still love her if she were not pretty. Then she slits his throat (the throat of the lookist patriarchy, it would seem).
At the very end she sneaks into her mother's house while the police are on the hunt for her and cuddles with her in bed, symbolizing the fact that the femcel rebellion against Stacy and moid oppression is now complete, but comes with a tragic price.
