write, this sounds like a very taxing situation.
needless to say, your friend is not thinking about your feelings and your health by pressing you. And I have a hard time seeing how you are going to maintain the friendship after she is married to this guy. I don't know the history, but it sounds like he is a jerk and you are just going to be waiting in the wings, biting back your tongue and picking up the pieces.
Before I got married, the night before, one of my friends told me not to get married. She said, you can still back out. She was so right, and at the time part of me knew it but most of me was just caught up in the tide.
I did not listen to her and she did not show up to the wedding. In fact, we lost touch forever. But I still think about her and I am grateful that she tried to save me.
I guess my point is, if you think your friend is making a mistake, say so. If it destroys your freindship for now, how was that friendship going to survive anyway? Once you say that you can't stand the guy, not just that he is not fun, but you think he is horrible, or whatever, she may not press you to attend any longer. Or, you can say that your therapist does not think it is a good idea.
Plucky