What I do if I realize I'm going to go to something, whether I like it or not :-) is let go of thinking about how much I don't want to go and look "forward" to the going and what I can "salvage." I think about the various people who are likely to be there, what I've been doing since I saw these people (what I can talk about) in your case, I'd be thinking how I could help the new American meet these people and have a good time, etc. In other words, I'd think of several things to "do"/think about besides not wanting to go. Just accepting that I don't want to go (and there's nothing wrong with that, it's not bad! You are allowed your feelings, whatever they are). If I couldn't get my mind turned around I'd give myself laser insight :-) and try to figure out just what is standing in my way, just why I didn't want to go -- what I was afraid of or who I was afraid of and why and what I could do to help myself in that "situation." Being a little "prepared" helps me, having a few things to say or even "warning" the person I'm with that I don't want to go and asking for their help! I would tell my companion what you told us, that you don't really want to go and feel you "should" because it's a good friend. I'm super honest :-) so would even tell my companion that I'm bringing her to help me :-) because I enjoy being with her more than I like being alone at the party. I'd make my companion feel as good as I could; that I'm going because I enjoy her company and want her to meet my friends, etc.

I haven't read any reply you've made yet so don't know you had a good time despite yourself (I hope :-)