@Bt
As a wise main once said: "Painis weakness leaving the body..." ;P
@Cz
If I were you, I'd still go, as it's an oppertunity to grow a lady's pair, or maintain those that you already have. Shure, (s)he'll be there, but you're strong enough to not care about that! Right?
Unless the reason why you'd rather avoid him is something more serious, such as assault, or stalking, I think that there's really no reason why you can't go to the party, and still avoid him at the same time.
(But that's just my say and encouragement)