Like some 'hot popular girls/guys' in high school who became nothing, what if that girl actually became a social wreck ?
Cause while we may take the 'vengeance' angle, and like Mila mentioned, Bella's taking revenge at unhealthy levels, what if that girl is part of Bella's personal growth ? Amber wants to help the MC cause he's good to Bella, pretty sure Bella forgiving Melanie (I think ?) could be a huge part of her transformation, a huge part in Amber's LI path, and a huge part in the MC's path to become someone 'nomal' again.
There would be a choice, of course, and we could also plan her vengeance and hurt her tenfold, but then everything could go down the drain... and the MC promised Nojiko and Nami he would stop getting into trouble, so yeah.
Just throwing a different, potential angle, cause I love Bella the same way I love Quinn (BaDIK), and there's a redemption arc for both of them somewhere.