You and your wife need to get in therapy now. If things have gotten bad enough that your wife is threatening to leave you, then there are most likely other aspects of your marriage that are suffering as well. It can be very difficult to be caught in between your “original” family and your chosen family, and you could benefit from having a professional counselor help you navigate your way.
The best way for your wife to rebuild trust in you is for you to be trustworthy. You need to prove to her that she comes first and that you understand how much she has been hurt. However, unless your family has truly been abusive toward your wife and daughter, I don’t know that you need to permanently cut off all contact with your mother and sisters, but you need to let them know clearly and consistently that you will not tolerate any disrespect. I hope that you and your wife can work things out.
All the best,
Dr. Holly Counts