But I suppose I find it hard to accept that my insecurities would prevent me from going somewhere where I really wanted to go.
Look, you have to obey your own limits. Your insecurities are flags telling you there's unfinished business at those marker points. Don't run. Examine.
You have found these things:
1) You are not good with the meta because of the cheating. I am not hearing any kind of apology/acknowledgement thing was made by her to you, the wife. I'm not hearing that you have asked your meta for one. You don't have to be best friends, but expecting polite to the wife is not unreasonable. Be nice to hear from meta that she's planning on keeping her nose clean and not ding DH anymore because at home? Then YOU are the one holding the emotional bag if she walks! Sheesh. Fresh.
2) Now you have to bear witness to their canoodly faces. That hard to bear when there's still #1 pending. You aren't going to get compersion feel goods by basking in his love light for her so you can go "Awwww... he's so cute when he's in luuuuuvvvvv!" when you feel all arghy about her. It is unfinished business there.
3) You went to an event that you normally attend with DH and overstayed your emotional limit. Even if things were GREAT with the gf and no cheaty stuff -- I think you would have felt sad about one of "your couple things" not happening this year as a couple.
So yah -- you learned some things for next time.
- Could have stayed briefly to support friend and left early.
- Could have brought date.
- Could have skipped it and sent friend flowers or something to commemorate occassion.
Learning to handle that one more gracefully comes at a price -- but now you know some good stuff about yourself and ideas for navigating it next time.
It's not a TOTAL loss.
Hang in there. You will feel better when it isn't so fresh. Remember to BREATHE.