How to tell your mother she needs to be put in a nursing home?

My mother is 92. She has Dementia. My mother is in a nursing home for rehab. She contacted pnemonia, and after her hospital stay they sent her to a home for rehab. Here is the situation: She cannot walk with a walker unless someone is hanging on to her. During the day she is in a wheelchair, then the bed at night. Some days she is coherent, other days not so much. She is married to a 92 year old man who is totally blind and still lives in their home. They have needed in home health care for some time but refuse it. At the home the staff are going to recommend to mom's doctor that she go into long term care at a nursing home. They also believe mom's home is not set up to accomodate her needs. My mother's husband has told her that she cannot come home until she can walk with a walker "without" someone helping her, and she cannot come home if she can't get out of her wheelchair to get to her walker. He told her he can't take care of her if she can't do either of these things. Last night when we went to see her she said she wanted to come home and asked her husband to let her come home. It was sad. He told her no, not until she could do the two above things. He is going to need to tell her pretty soon that she is not coming home, and I'm sure he is dreading it. I was wondering how do you tell someone they can't come home.