I totally understand this, I have a wedding coming up myself. There are always so many people I don't like and can't stand I know I'm going to wish I hadn't gone almost the second I get there, but as it's a family wedding of course i'm expected to go, plus I want to show my support for my aunt whose getting married as she's been a big part of my life. My old T taught me a trick called seven eleven breathing to calm me down it slows your heart back down too, you breathe in for seven seconds, then breathe out for eleven. So when I start to get anxious I do this to try and calm myself. It also gives me a bit of a distraction because I can focus on the counting other than whatever is worrying me. Maybe try this out and see if it helps? At the end of the day, you have to think about your own health and what you want. If you really don't want to go then I'm sure your friend would be understanding if you explained.