It sounds like your wife is a big part of the problem. Her reactions to your daughter sound borderline abusive, and certainly emotionally damaging. What your daughter needs is unconditional love and understanding, not yelling or threats. Since her mother certainly is not providing a soft place to land, she needs therapy all the more. It sounds like your wife could also benefit from being sat down and told how destructive her behavior is to her daughter. I hope you will help provide a buffer between your wife and your daughter, so that the child is protected.