Alright dude...

Well this is my opinion on the matter.

You were pissed that she was even going... You planned on blowing up... I would have too...

Well anyways you arent over reacting... she promised... she broke that promise she deserved a bitchin...

But after a while you 2 should both get over and fuck...

Well anyways As someone said earlier with "girls" if you are out of sight you are out of mind...

If your with a "woman" then your always on atleast one part of their their mind and you cant do what im about to tell you to do.

Since your with a "girl" your out of sight out of mind...

Next time she is going to ANY type of party just simply reply
"Ok honey im going to "insert name here"'s party and talk to you later"

She will probably flip out and because you KNOW what shes going to do at that party anyway just lat her worry and fret and nothing will happen between her and another guy at that party she will be to busy worrying if you are out fucking some other girl...

Thats my two cents.