He is friends with the girl he cheated on me with?

I really need some help/encouragement!!

So, I've been seeing my ex, who cheted on me a year back. (please do not attack me for staying in contact with a cheater, it's a lot more complicated than it sounds.)

The only problem I've had with him is that he claims to be bff's with the girl he cheated on me with. I haven't confronted him with the issue because we are not together yet, even though he does say he loves me.

This friday he had his birthday party at his house, and he had invited me and the girl. But only a day before the actual party, he told me he's not sure if he wants me there. The reason was that he was worried I'd attack the girl bff on sight. (i mean, i do hate her*, but??) After I told him that's not case and that even if I do hate her, it's his speacial day and I'd never cause any drama to ruin it, he told me not to come because he "wasn't sure if the girl bff would approach me somehow". He knows I'm not a violent person, so I was quite upset.

I'm no way jealous in relationships &I've never in any way limited his friendships from him. I personally don't think it's okay to deny any friendships from your partner, but this one I can't accept.

*=When I found out about him sleeping with the girl, I had the worst anxiety attacks of my life. The girl knew my boyfriend was dating me, and also in many other ways sabotages our relationships. The absolute worst anxiety attack I've had was caused by something she said to my boyfriend, and mh boyfriend then said to me. From what I've heard, she has been struggling with anxiety too, and has been cheated on/in an abusive relationship. Yet she was still willing to do the same for me, and for that I hate her. (had to clarify bc sometimes the third party might not be to blame).

So my question is, is it acceptable for me to cut ties with her if we ever get back together?? I think I have a good reason for that, but I feel like he wouldn't listen. I don't usually make such requests so idk.