Name and some small details changed to avoid outing.
Close friend is turning 40 soon.
Party is being organised by and held at the house of another friend of hers, we'll call the organiser Mary.
Mary has invited her wider circle - I'll call them ' The Group'. Mary and the group all live in the same neighbourhood and do all their socialising together every weekend. Basically all couples (and one single male) in 30s and 40s and tbh quite cliquey and closed to outsiders. My friend and her DH aren't part of the group but on the periphery and getting friendlier with them in recent times. I'm not part of it either but we used to sometimes be all at same events due to mutual friends etc. I should mention some of the group knew my ex h who I divorced a few years ago due to emotional abuse. No one knows about this abuse and exh played victim very well. He's no longer in same town.
A year ago when single, I was at a party where many of the group were present and got talking to the only single guy in the group. We then dated for a bit and I thought he was nice. I began socialising at some of the group events a bit more and thought I was being accepted.
We were all at a concert and while I went to the loo, I found out (the following day) the supposedly nice guy I'd been dating was slagging me off and disrespecting me to the other men and some of the women in the group, presumably they all believed my exh version of me and had no respect for me. I only found out as one of the men is cousins with another close friend of mine (she's not part of the group at all though and isnt the birthday friend either) and he decided to tip her off so she'd have a word with me and warn me off the next day.
She did warn me off but she did it in quite a telling off way as if I'd done something wrong. As if it was my fault that he disrespected me. It was humiliating. When I was with them at the concert they were all nice to my face then I find out its different behind my back and I get a dressing down for it from my so called friend. She basically said I'd been too loose following divorce and they all thought I was 'easy' so he was only dating me for this reason. I dated a few people post divorce and thought I'd been discreet about my private love life but friend said they social media stalked me and seemed to know who I'd dated previously. I had no idea of any of this and I thought single people were allowed to date other single people in peace without judgement. Obviously not.
Anyway that whole saga really knocked my confidence and I was very upset by it. I vowed to stay well away from all of them and that includes this birthday party.
I told birthday friend I didn't feel comfortable going due to what happened and can I take her for a meal out instead to celebrate. the whole group will be there and it's in their neighbourhood. She's said I'm selfish and oversensitive and can't believe I'm doing this to her. AIBU?
BTW I appreciate how high school this sounds. Had I know how toxic they all were I never would have gone near any of them. I think I need to cut ties with the lot of them tbh but just wanted some more perspectives as I'm quite emotional with it all.