I have avoided my ex like the plague since the break up back in September (an LTR of 4 + years and engagement that she broke off, only to find a new bf less than a month later).

I almost walked into a situation where I would have ran into her and her new BF this weekend at a grad party I now will not be attending (didnt really want to in the first place).

Had I not viewed the invite, went, ran into her, how should I have acted?

I dont want to give off the impression we are friends, but i didnt want to make it overly apparent to everyone that I dont want anything to do with her (huge risk of losing my frame), and I KNOW I would say something mean to her BF (who is smaller than me).

EDIT** Thank you guys for the awesome advice on this subject. I can hold a good frame but I have always wondered what I would do in a frame breaking situation like that, one which seems like its going to happen eventually.

Just looking for some advice on the hypothetical because when it does happen i want to be prepared. I have just avoided her at this point.