Yeah, leaving the cheating part aside, it was very nasty to do. I can't recommend whether to tell your friend or not because I don't know her so I don't know how she would react. It's your choice really. But think of it this way: If he tried it on with you, what's to stop him trying it on with someone else? I suppose you could stop it all right now...

I just noticed that this bit "If he tried it on with you, what's to stop him trying it on with someone else?" sounded like I was slagging you off. I wasn't.