Well I agree with all the others, You and your wife need to set the rules and expectations straight with everyone. Disrespect towards a parent should never be tolerated, while at the same time the kids are people too and deserve fairness. I would suggest you and your wife meet with a professional together to discuss ways to improve your parenting skills in a blended famly. Then you and your wife can implement together Just how this family WILL function, they (the kids) need to know you support each other, and you both care very much for everyone to live together in a happy functioning family. It Sounds like your wifes daughter has serious issues with her behavior, and she too would benefit with some therapy if needed. Best wishes that you get through this difficult transition.