Help! My husband of 8 years is driving me crazy with his 15 year old daughter.

She has lived with us and my 12 year old son on and off. She is a good kid but her father/my husband is so over proctive. He only want to spend one on one time with her. It is all the time not sometime. He talks with her in private and never tells me how she is doing in school etc. then at the end of the day he wonders why I am so cold. I dont; want to be her mom but I want to feel like I can walk around freely in my home. Please help me should I just let it be or do I just walk away from this marriage, he is not going to change and my feelings arent changing. He even talks privately with his 20 year old daughter on the phone and I always ask him how his older daughter is doing and all I get is FINE.