My two best friends A (girl) and B (guy) have been together for 6 years. We all met 1 year ago and since then we’ve been inseparable. I hang out with them about 3/4 times a week and they’re like family to me. I have to add to this that we are all super kinky, swingers and go to a lot of fetish parties together (that’s actually how we first connected).

Now A and B frequently have threesomes/foursomes/orgies, you name it. I don’t have a boyfriend at the moment so I either tag along, meet someone/watch or they just tell me all the dirty details and pictures/videos afterwards. Even when we hang out we’re all always cuddling super sensually/kiss each other etcetera (we’re all bi) but we haven’t had a threesome yet although both have told me that they want to (which I’m happy to).

Last week we went to another fetish party but A couldn’t come last minute as she was leaving town for a week. She told us to go anyway and we did. Nothing happened at the party between me and B (only with others) but we ended up taking lots of drugs (mainly ecstasy) and went back to their place (I always crash there on the weekends). I was incredibly high and don’t remember much but I know for sure that we ended up having sex. I remember asking him if it’s really ok for A and he said “I know she wouldn’t mind cause I know she wants to play with you too”. And like “let’s do the 3some when she’s back” Anyway I woke up and felt absolutely horrible and full of guilt. B flew out to see her this weekend, they went to a friends house, had another orgy but ended up in a massive fight to the point where they haven’t been talking for almost a week and blocked each other (the fight was about money and work). She sent me some pictures from her “fun” party and i asked her if she’s finding anyone interesting and she said “not behind his back” which now makes me feel even worse. He is back now and I told him how I feel and stuff and he says with the state their relationship is in right now after this fight this is not the time to tell her.

Even though we all are as poly and pervy as we are, I still feel like lines were crossed and feel absolutely horrible, mainly because she doesn’t know or wasn’t involved/in the room.
I am unsure wether or not I should tell her or if we should just all have a threesome and write it off.

Genuine thoughts/advice appreciated.