There's a guy I know - let's call him Bob - and I found out that Bob had cheated on his 17 year old fiance. Bob is 24. I know for a fact that Bob kissed another girl at a party. Bob also had this online dating profile (which he accidentally showed me) - and on his profile, he said he was tired of being in a monogamous relationship, and he was looking for hook ups. After I started picking on him for the profile, he came up with this random story on why he has a profile on there, and he proceeded to delete it - I told him I didn't care and it wasn't any of my business.
I wasn't gonna intervene in their life, but I'm beginning to get to know this girl and she wants me to be one of her bridesmaids. She's only 17 and I just can't stand back and watch her make the mistake of her life. She's so young! And the lying sleazebag of an asshole Bob is so much older than her.
Me and her actually had a conversation about guys and cheating. To her, kissing definitely counts as cheating. You might say that maybe he'll change, but she deserves to know - don't you think? And honestly, I really don't think he'll change. I never liked this guy anyway. The only reason we hang out is cos we have a lot of mutual friends.
Oh and did I mention that Bob is not a US citizen, whereas his fiance is American?
What do you think is the best way to deal with this situation?