What would you do

My buddy just the other week told me he broke up wit his women because she liked someone else(so she said), i was like why she like him, he was like because i am diffrent then the way i was with her before i was like then be who you were before he said it aint that easy… anyways to get to the point she told me that she had sex with the guy she liked and regrets it but she did it more than once(Women god) now she is saying that this guy will never be the same as my buddy and blah blah, and wants them to work things out. What would you do?? when he finds out she slept with the other guy do you think he should still work things out or forget the b***??