Nellie is a primary character and serves as one of the narrators. She is a 17-year-old girl from one of the wealthiest families in her small town. Nellie is privileged and entitled but also lonely. She doesn’t have any real friends and knows that the other teenagers only tolerate her because of her mother’s social machinations. Nellie is insecure about her appearance, especially because both of her parents are extremely attractive while she is merely average. Nellie is often resentful of her mother’s overbearing presence in her life, but she loves her father.

Nellie’s character is defined by her intense, erratic emotions. She immediately hates and resents Jane because the other teens like her. She develops an intense attraction to Luke, even though he doesn’t reciprocate her feelings. As a result, Nellie is constantly jealous of anyone whom she perceives as a rival for Luke’s attention. Since she does not know the identity of Luke’s secret girlfriend, Nellie is jealous and hateful towards both Blair and Jane. As Nellie is lonely and has difficulty forming social and emotional connections, she bonds intensely with anyone she thinks relates to her and becomes vengeful when that person turns against her. Nellie has a long history of malicious and at times violent behavior, which establishes her impulsivity and lack of remorse.