AITJ for telling my dad I don't want his girlfriend at my college graduation and that if she comes I won't walk?
Some background because I know this will sound harsh without it. I'm 22F. My parents divorced when I was 15 after my dad had an affair with a woman I'll call Karen. He moved in with her about three months after he left, which meant I was watching my mom fall apart in real time while he was essentially already moved on. I never said he couldn't date, I'm not a child, I understand how people work. But Karen specifically made things worse during the divorce in ways I won't get into, and I've never been able to get past it. I've been civil to her at family events for my dad's sake but we have no relationship and I've never pretended otherwise.
My graduation is in six weeks. It's a big deal to me, I worked really hard for this degree and it took me an extra semester because I had to take a medical leave sophomore year. My mom, my grandparents, and my two closest friends are coming.
I told my dad a few weeks ago that I'd love for him to be there but that I wasn't comfortable having Karen at this specific event. I wasn't mean about it, I just said this one day is really important to me and I want to feel relaxed and present, not tense. He got very quiet and then said he "doesn't go places without her anymore" and that it wasn't fair to ask him to choose. I told him that I wasn't asking him to choose, I was telling him what I needed for my own graduation, and that if he brought her I genuinely wouldn't walk becuase I didn't want the day ruined. He called me manipulative. My stepmom thinks I went too far with the ultimatum.
AITJ for making this a condition or should I have just let it go?
TL;DR: Asked my dad not to bring his girlfriend (who was his affair partner) to my college graduation. He said he won't come without her. I said then I won't walk. He called me manipulative