For about a year after I separated from my AH, I was angry at alcohol. It had taken away my husband, my dreams, the life I so desperately wanted. I couldn't stand to be around it in any way, shape or form for awhile.
After some time, I found I could tolerate going for drinks after work with friends, or to a dinner or party where there was alcohol. I still didn't want any myself, but I wasn't too angry to even be around it anymore. These days, I enjoy a glass of wine or a cocktail on occasion.
So, my anger at alcohol has diminished, but I still am quite uncomfortable being around anyone who is more than a little buzzed. If I find myself in that situation, I remove myself quickly.
What I'm saying is, maybe you don't have to have a "line in the sand" kind of boundary that you announce to your friend. Maybe you only need to discuss that with yourself, and make sure you remove yourself from any situation that you are not comfortable with. No explanation needed.
L