The Good @inuke
You should tell her. She is your friend and you care about her. But hear him out first. Let him explain himself before you go to her. Once should make absolutely 100% sure before making any call on such decisions. After all, it is a matter of concerning two people who are bound to get married. He may lie and tell some bullsh*t story just don't fall for that. Either way, this has to be reported to your friend.

The Bad @inuke
It has been 9 days since the question is raised mostly you probably had taken a decision and my opinion doesn't matter. 

The ugly @inuke
Well, you should tell her. Not because that is the right thing to do or because if he is this way before marriage, Imagine how he is going to be after marriage. But purely for the sake of ass-kicking. Imagine yourself and your friend ganging up and laying a beating on that guy (who deserves every single flower pot to be throwned at his).


All we are saying is that tell her It is the right thing to do...