<human>: Can you succinctly summarize the text in 1-3 sentences?

My fiancee is having a hard time with a situation regarding her former best friend and said friend's impending wedding.
Her friend has a very lax attitude and lets most things slide with very minimal thought put into it, and this has caused her wedding party to be thrown together and clash.

Specifically, putting my fiancee in with her abusive ex boyfriend and his jealous and weirdly stalkerish baby Momma.
My fiancee doesn't want to have all of her past anxiety flair up just by being around him; but her friend has told her if any problems arise whoever starts the drama is kicked out of the wedding.
The issue is, for the last couple of years my fiancee and the bride to be haven't really been close at all, and this request for her in the party is based purely off of history and my own friendship with the groom.
(We set them up, we used to be best friends with them, I with he and she with her).

Sorry for the blah blah, she's stressing out and can't sleep so I offered to ask Reddit for help and am now throwing together this post.
<bot>: Fiancee used to be friends with bride, abusive ex is in wedding party and fiancee doesn't wanna deal with it, and feels the wedding invite is based on anything but a current friendship.