If she is so awful, why does he have ANY contact with her? Unless they have minor children, WHAT do they argue about? When will he cut off contact? When you get engaged? Married? Never? Truthfully, he sounds like a great pal to go bowling or fishing with, but there is only room for TWO people in a relationship (unless that's OK with you). Sorry to be so harsh. But YOU dont have to do anyting. He has to choose.