Lizzy was once a nice and friendly person until her family was broken up due to her father having an affair with Miss Kara, the mother of one of her classmates, Claire. She suffered a psychotic breakdown, turning her into a sociopathic “monster” due to her inability to reconcile and deal with her grief over the situation.

However, these events were triggered when Kevin showed Lizzy evidence that her father was cheating on her mom, which made her feel humiliated and enraged, wanting revenge against Miss Kara, Claire's mom

So, accompanied by her friend Petunia, she brutally murdered Miss Kara and framed another of her lovers for the crime. Feeling that this wasn't enough, Lizzy decided to take revenge on the woman's family to complete her vendetta, and so the two waited a year before putting their plan into action