Tough one isn't it. Damned if you do, damned if you don't. I've told a friend before & even though she said she was glad I told her, her cheating ass bf got very hostile & threatened to beat me up. (He was such a nice man wasn't he!). And they stayed together anyway... Personally if I was being cheated on I'd want to know. I'd be mad if a friend or relative knew & didn't tell me. To find out down the line. Especially if it was an on going affair. Knowing my husband was or is still sleeping with someone else, whilst still being with me! No grey areas for me it would be the end.

If I've learnt anything from letting someone know about a cheating partner it's don't... You won't be thanked for it and you'll be blamed they may leave them but you always be the person who ruined their lives and most the time they'll never leave that person although you always feel you should tell them like I said you'll never be thanked for it although I would want to know and wouldn't blame that person if your saying the wife is too stupid to leave him maybe your better off letting her find out herself or if you feel you have to then tell her because it's not worth having on your mind if it's going to cause you anxiety and agg X