Your fiance is the one who needs to handle this, not you. I don't believe I"ve ever quoted the Bible as advice on here before, but this PRINCIPLE is true. In Genesis it says that a man shall LEAVE his father and mother and cleave unto his wife, and they shall be one flesh. Ok, He has TO LEAVE HIS MOTHER AND FATHER. He is no longer a part of them, you and him are now/will soon be one. If he doesn't take care of this soon, I'd seriously reconsider. If she's like this now, imagine how she will be for the rest of your lives. MISERABLE.