Mom has dementia and her behavior is getting worse. Any advice?

Mom never liked my husband and after 23 years of marriage she still hates him. She's 77 years old and has dementia, she was always complaining of living alone so I brought her from NJ to FL live with my family a year a ago and it has been a disaster from the get go. I love her and I try to take care of her the best I can, I do everything a care giver does for someone they love but she's not helping; always complaining about every little thing, budging into everyone's life but the worst part is the things she's making up about my husband; like when she sleeps a lot is because he's putting something in her coffee (even though she's by herself most of the day), if her eyes are irritated is not because she has allergies but because my husband "sprayed something in the air" to irritate her eyes; everything that happens to her is my husband's fault. She lies, and manipulative, when I confront her about her behavior she starts crying saying that no one loves her and she has no place to go. My daughters (22 & 16 years old) that used to lover so much now resent her, my 22 year old that still in college is thinking to move out of the house. I tried to find her a place near by where I can keep and eye on her and she said that she's not going anywhere, that I'll have to drag her out the house for her to leave. My husband has been great through all these problems but I don't know how long more he'll be able to put up with this situation.
She always been a difficult person to live with, god knows I'm not lying, but her behavior now makes me think she might not be mentally stable. I just made an appointment with her doctor to ask him a recommendation for a psychiatric evaluation. I'm at my wits end, any advise?