Asking to "go home" seems to happen at some point in almost every person with dementia.
However it started, I have a feeling that it is contact with family that is triggering the behaviour.
When I used to visit mum I have actually witnessed a lady who was happily chatting to staff and other residents when her daughter arrived to visit. As soon as she saw her daughter it was like a switch flicked over. Suddenly she was crying and begging her daughter to take her home, telling her how much she hated being there, that the carers were horrible to her etc etc. As soon as the daughter left, within a couple of minutes it was all forgotten and she was back to laughing and talking to the carers again. It was astonishing - unless I had seen it myself, I dont think I would have believed it.
The thing is that when people with dementia forget, they forget the incident, but they remember the emotions. So, after you and your mum have visited , although she may forget you have been, she will remember the emotions and then when she sees you again the emotions will resurface. Its difficult to know how to handle this, but although this might sound mean, if you dont visit for a couple of weeks it might break this link.
We actually reduced the visits. We only see her two times per month, basically every two Tuesdays.
I suspect we are also the reason.