AITA for telling my former friend why I hate her?

I was recently talking about an ex-friend of mine who I ended up "breaking up" with in middle school. She cheated on her bf with my crush, and he broke up with her. Then she tried to cheat with my crush again, so I broke up with him. He eventually realized he liked me and not her. <br><br>I have not spoken to her since middle school. A group of us were having lunch together and one of her children was there. She came over and tried to include herself, but I wasn't having it. I told her that I had no interest in talking to her, that she cheated on her bf with my crush, and he broke up with her. Then she tried to cheat with my crush again, so I broke up with him. He eventually realized he liked me and not her. <br><br>She was like "oh yeah I remember that" and I said "well, that's why I have no interest in talking to you. And you have a daughter older than the one here, so she must have a father, which means you cheated on him." She got really quiet and walked away. The rest of our group was looking at me weird and asking what the fuck was wrong with me.