My friend cheated on her husband and lied about it

So a friend of mine, a friend I've known since high school, cheated on her husband a couple weeks ago. When she called to tell me about it, and that her husband found out, I was floored. When she confirmed it was her ex that she has never been able to let go of for over 20 years, I was pissed. HE is married too and has multiple affairs on his wife. He even cheated TWICE and broke off the engagement to my friend TWICE because he cheated.

When her husband asked who it was she cheated on him with, she lied. Gave some random name that I'm not sure was real or made up. She never clarified when I asked, and I told her I needed to step away.

She plans to keep this a secret because, as she put it, she's dug herself a hole and keeping it a secret is the only way she can see digging herself out of it with her soon-to-be ex-husband and her kids. All her kids are older. Her youngest is a senior in high school. They are not happy with her, but mainly the kids she has with her husband NOT the kid she has with her ex. I think if they knew who cheated with, they'd be horrified.

I guessed right away as did a family member when she told us what she did. I maintain that if she keeps this a secret and it comes out later (these things have a way of coming out!) then it will be worse for her because she lied about it. She cheated and her husband found out 4 days later - how the fuck does she think she can keep this a secret?

Our lives are so intertwined from all the years of being friends and now I find myself questioning what I thought I knew about her. I find myself reaching into the past of certain things she has done - cheated on her husband emotionally with her ex through the years (also sent scandalous photos to him), and developed a crush on her husband's bff because he reminded her of her ex.

I keep thinking about how she snapped at me when I asked who she cheated with (even though I knew immediately) and she said "Does that really matter?"

And I find myself getting pissed when I think of how she got mad at her husband for throwing out stuff she gave him when he was packing up his crap and called him "cruel" and said "Happy people don't cheat".

I am just disgusted by all of it and part of me doesn't want to throw our decades worth of friendship away, but the other part of me can't help but see her completely differently. I am disgusted by all this.

I don't plan to tell anyone in her family. If I was asked I am not sure I would be able to lie, but I don't think I could tell the truth either because that is hers to tell...I am conflicted I guess. I don't see them asking me though.

I'm kind of all over the place with this mess. Anyone else go through something similar and have to take into question their whole friendship? I'm going to assume so since this is the Toxic Friends subreddit lol.

Thanks for reading. :)