I(F20s) have a partner who cheated on me with multiple people. I contacted one of the said partners because I wanted clarity. They attacked me for being a "nasty ginger" and they "are hot and blonde and I need to get over it because he will only think about them" (whenever he was cheating on her the whole time as well)
Initially, I confronted her because I thought he was cheating with her again, but once she stopped trying to bully me she confirmed it wasn't her. She apologized for actions but I kinda still hold it against her.

I honestly think I still might be with him because I know that it makes her rage on the inside.. 
I don't know why but it felt empowering to know he wasn't responding to her whenever she tried to reach out multiple times because he was trying really hard with me for once. 

It's clear now he hates her, so I don't have to worry about him ever contacting them again. She leaked all his nudes to me and he became angry about that. He said he doesn't want that person ever in his life again and he swears he only ever talked with them because he was under the heavy influence of drugs and alcohol.

I think I mostly stayed because it felt good to read her posts about claiming she wanted to harm herself and she kept trying to contact him and her boyfriend (yes she also cheated on her boyfriend the whole time too) got her help. 

It makes me feel evil to feel relief that he truly doesn't care about her anymore.