Should I tell my friend’s wife that he is cheating?

A few days ago I asked my friend why his oldest daughter seemed to be stressed and losing weight, he then told me that his daughter knew things no one else did, he told me he has been cheating on his wife for about 8 months. He tried to use me as a third wheel to meet with that other girl. I refused because I felt that what he is doing is wrong because he has 4 kids with his wife already and his decision could really messed them up. Now, his wife…she’s is not the best, she is a hater, she is bitter most of the time and let’s just say that she always treats my friend like shit. She has never liked that I’m still friends with her husband and has treated me very badly. In this case I don’t know if I should tell her because 1) I don’t really give a f about her but 2) i worry about the kids especially the oldest of their daughters. I talked to her and she is so stressed about her parents divorcing, she said she feels like she is betraying her mom…I mean, it really broke me to hear her say things like that. What should I do?
Should I tell my friend’s wife that he is cheating?
Updates
1 y
I forgot to mention, their daughter asked me to talk to her mom. I had full plans of staying out of it. She called me three times today asking me to do it because she knows when my friend goes to see the other girl. I’m just worried because this girl was 130lbs, now she’s 75lbs and it’s not healthy at all.
Should I tell my friend’s wife that he is cheating?
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