I am so sorry. I also had a double betrayal (actually a triple betrayal - BFF and her husband were polyamorous and were both in on the affair with my WH). I was also totally clueless about what was going on, and was also attacked and blamed after the fact by BFF and her enabling husband. However, I refused to let them control the narrative in our social group, and I outed the fuck out of all three of them to all of our friends after I found out. I got a lot of social support because I did that, and it made it a lot harder for them to paint me as the bad guy to everyone else we knew.
The double betrayal is one of the worst kinds of affairs, IMO. Not only are you blindsided by your WS, you have nobody else to even turn to in your horror and grief because the other person/people you trusted the most are "in on it". For me personally, it has been the worst thing that ever happened to me in my life. I no longer feel that I can trust other people, am no longer interested in making new friends, and I was quite extroverted and gregarious prior to my husband's affair.
In fact, I am 6 months out now, and even just this morning I was still ruminating about my friend's role in this. She never apologized or even gave me an explanation, just a horrible attacking email telling me what a terrible person I was for not wanting my husband to fuck my friend or to be lied to.
5 year friendship down the drain, and I still have no idea why she or her husband thought it was ok to treat me that way. I kind of wonder now if she just secretly hated me the whole time and was just biding her time until she could find a way to injure me. Because why would anyone do such a thing to anyone they actually liked? It's really crazy-making. It's still making me sick and sad all these months later.
My husband has been a model wayward, very remorseful, went NC in the first week after the affair fog lifted and he never looked back. He now says he feels repulsed by thoughts of her and what he did. We have moved out of the city where it happened, are trying to reconcile, and we do have some good days now along with the bad. But I will never, ever get closure with my friend and her husband. It will haunt me the rest of my days. I cannot imagine ever inviting another female friend over to my house again, hanging out, going on vacation with another woman and my husband, etc. I am 39 years old and will probably never have another female friend again. It's too frightening to me to think about how little we really know people, so I can't risk it. She helped wreck my life, utterly betrayed me as much as my husband did, wounded me to the core, and I can't take another chance on someone like that again.
Anyway, you are not alone here. I am so, so sorry this happened to you. As other people have said to me, your BFF and your husband are vermin. You didn't deserve this. They took advantage of you and your trust. It's not you, it's them.
Down in the section called "I Can Relate", there is a thread for those of us who are (sad, unwilling) members of one of the worst clubs in the world: the Double Betrayal club. Check it out if you feel up to it.
*HUGS*
ON EDIT: By the way, if you want to read my story it's in my profile, and there are many others here who have stories similar to yours. You are not alone, you are not crazy, and you weren't the first or only person this has happened to. Plenty of good people are betrayed by sick, unethical assholes with emotional problems - people who have good marriages, bad marriages, young, old, sick, healthy, beautiful, whatever. Being a "certain kind of person" or having a "certain kind of marriage" is never any proof against infidelity. It's NOT about you. It's ALWAYS about them and their shitty coping mechanisms.
[This message edited by TheGarden at 11:18 AM, December 29th (Sunday)]