If you must attend the party, be coolly civil. Answer direct questions with succinct answers that do not invite further conversation, then find a reason to be elsewhere. Practice what I call the Crystal Gaze. Basically, you're looking at someone, but you don't see them. You are looking through them as if they are a pane of glass. They're hardly even there. And all the while keeping a completely serene expression on your face, a smile that shows absolutely no teeth, just an upward quirking of the lips. It says, "I'm smiling at you, because in my head, blind mole rats are gnawing on your cankles."
Seriously, it's terrifying.