she's evil and sadly i can't look past that
Which one? Girl who chose to cheat on her boyfriend (tbh, she doesn't even seem to care about him), or girl who seduced her old flame after breaking up? :)
Honestly, this seems kind of inevitable setup because it's just about two people who are deeply obsessed about each other. That's what takes some points away from my evaluation, because it's largely stakeless and coded in result.
Best cheating stories are ones with pressure, doubt, clouded motives, uncertainty of timing and so forth. Where you genuinely can't tell where they story will land even at midpoint in chapter 69.