Friend A has been with her partner for over a decade - they're not married and have no DC together. She's spoken to me at length about feeling unfulfilled - her partner takes her for granted and puts her down a lot, but she has such low self-esteem that she can't muster the strength to leave.
Friend B has been with his wife for a similar length of time. They have 1 young DC and I thought they were happy, even though outwardly they seem like chalk and cheese - he's loud, extrovert and over the top, whereas she is quiet, down to earth, and far more of a homely.
At another friend's recent wedding, I walked into a side room and found A & B kissing, with B's hand up A's skirt. I was so shocked that I walked straight out again and didn't say a word.
Now A is carrying on like nothing happened and B is actively avoiding me. The drinks had been flowing and I'm inclined to think it was a one-off rather than an ongoing affair, although I can't be sure.
However, I feel so bad for B's wife. She's a lovely person who would be devasted if she knew B had betrayed her. If it was me, I'd want to know if my DH had cheated and part of me feels I should tell her, but I'm closer to A than either B and B's wife, and telling the truth would feel like betraying that friendship.
WWYD in my situation?