>>60331668I would use Ayatsuji's route in Amagami (the visual novel is better than the anime) as an inspiration for rrat!Ayame.
In front of other people, Ayame is a lovable goof that is adored by everyone as the cutest girl in the school. But in reality it's all an act that she is doing because she is addicted to all the attention and love she is showered with, and because she can live her life on easy mode thanks to essentially having an army of slaves (male classmates) willing to do anything to please her.
Then you catch her exposing her true self and from then on she drops the act when it's just the two of you: she is openly lazy, talks shit about you and everyone else, blackmails you into not revealing her true self (without you even contemplating the option of revealing it to others) etc.
Personally though, I would also prefer that deep inside Ayame has a good heart and not make a malicious Ayame hate fic. She could go through a redemption arc (thanks to your influence) where she drops the good girl act but turns over a new leaf and stops taking advantage of others. The boys would feel betrayed and the girls would see this as a chance to bully her.
