She is leaving the house, packing her clothes, demanding to leave and just won't let up. She is mean as usual, having temper tantrums and being just plain old defiant. Some of this has happen before, but this is more extreme then it has ever been and I am not sure what to do.
Anyway. Partly I wanted to sympathise with the head-banging frustration of this. And partly to point out that my mother had had years, not weeks, to adjust to her new home and yet she was still quite sure she didn't live there - so it's wouldn't be surprising if your mother is much more disoriented. I'm sure you will have realised before the move that it would create quite an upheaval in her mental state - I'm not saying it wasn't the right thing to do, just that you will have been prepared for this on some level so it's a matter of holding tight to the plan and riding this out.
What is your mother saying, exactly? That she's going home? Just that she's leaving, without saying where for?
I'm not one for lying to people with dementia normally, but if necessary so that you can both get to bed tonight tell her that she needs to stay here tonight - which is true! - but that you can work things out in the morning.
Avoid contradicting or arguing with her. You will frustrate her even more, with no hope at all of changing her mind or convincing her that she is at home.
Check for a u.t.i., I agree (it's always worth ruling out), but given that the move is recent and this isn't really a marked change in her behaviour I think it probably is more the disruption that's wound her up like this.
I'm sure many will advise asking her GP to help her with her anxiety. Again, I do think that's something you might want to think about.
Let her pack a case if she wants. Tell her you'll put it by for collection and then pop it out of sight (and with any luck out of mind) somewhere.
Anything you can distract her with? Favourite TV programme, dinner, a regular call to the family? What was her typical Sunday evening routine before?
OR, you can change the conversation -- 'let's go for ice cream'. (if she likes it) She may get excited about an outing and let the other stuff go. She may be scared and frightened.