I went but left before the gift exchange. Two of the administrators showed up. It was tense and everybody kind of paired off.
As for the questions:
administrators have shown up in the past but not by invitation
busybody is a peer but she is in very good with the administrators
I'm annoyed that they were invited but even more annoyed that she decided unilaterally to invite them
We had a faculty holiday party last week, this was just our small department. None of the other dpts were invited because they have their own get togethers
Thanks for the advice. Just glad it's over.