My mother and step-father are living with me. My mother has dementia. My step-father has memory and mood problems. He wants to take my mother and live elsewhere but my mother doesn't want to go with him. What rights do I have as a daughter to ensure that my mother remains with me?
Has your mother ever been declared to be incompetent, in the legal sense? Have doctors stated that she cannot make decisions on her own behalf, and has a court decreed that? If not, it is your mother's choice where she lives.
Do you have your mother's medical power of attorney (aka healthcare proxy)? This is often stated in an advance healthcare directive. If you have this authority and your mother can't make her own decisions, you can decide where she will live.
I think a visit to an attorney who specializes in Elder Law is justified (using Mom's money). This would be to set up financial and medical Power of Attorney documents, perhaps set up a caregiver agreement and/or room-and-board provisions, maybe get her will in order, etc. Mom can do these things with dementia as long as she still can understand what she is doing. She doesn't need to remember what she ate for breakfast, it doesn't matter if she sees little green men on the lawyer's bookshelf, it just matters if she understands that if she signs these papers you will be able to make decisions on her behalf. Elder Law attorneys typically make house calls. I had worked everything out in the lawyer's office and then she came to our house for my husband's signature.
This really isn't about daughter vs husband "rights" -- it is about your mother giving authority to someone to make decisions. If step-dad is her current POA, she can easily change that to you, if she is competent to know what she is doing.