1) I know a number of gay people who devoted a lot of time to straight sex because they thought they should, even though straight sex was essentially nauseating for them - they just thought it was supposed to be that way.
I don't think any of us know what your W's 'true nature' is, but my sense is that she's probably telling herself she's really gay, and she's probably rewriting your M history in a way that denies she had good sex with you.
But it really doesn't matter - your W wants D.
2) Alas, my experience is way different from yours. One day my W finally understood that she had betrayed herself by cheating and decided to stop. She revealed her A that same day and immediately became a model WS (whoop-de-do), and she's stayed the course.
3) I believe very strongly that BSes who deal with homosexual As have to process the same stuff as other BSes do. IMO, the gender of the ap has +es and -es WRT recovery.
For example, outside of the BS community (maybe inside, too, but I've never heard it) a lot of people think that our WSes had gay As because the male BSes weren't manly enough and the female BSes weren't womanly enough. I think that adds to our shame - but all BS shame is, well, BS (bullsh!t), and we have to heal from it anyway; this just makes it a little harder for us.
OTOH, male BSes have absolutely no cause to fear the ap was more manly, and female BSes have no reason to fear the ap was more feminine. That's a big relief, IMO.
So I think BSes are BSes, and I encourage you to read in the R, G, and D/S forums to find info that you can use. I think you'll find a lot.
At the same time, there's a thread for BSes with same-gender aps in the ICR forum. Some people think there really is something unique for BSes with same-gender aps, and you'll probably find good info there, too.
Remember, it takes 2 to make a good M, and your W wants D. It seems pretty likely that you can't have a good M with her.
Since we're in R, we haven't had to say anything to friends, so I have no advice for you.
I do know that when a friend came out in the '80s, society was different. He didn't lose many friends. Personally, I figured I was already tainted by being this guy's friend, and I'd be tainted even if I dumped him, so W & I happily kept the friendship going.
Besides, he was a friend, and I like my friends to be happy.... I suspect at least some of your W's friends will stick with her, especially since the stigma of homosexuality is less powerful today than 30+ years ago.
But that's her problem, not yours. Yours may be dealing with mutual friends who drop you and mutual friends who helped her cheat.
You may have to make new friends, but that's something human beings can do.
Bottom line: you can survive and thrive.