Hi
@Gill17 and a welcome to the Forum from me too. I moved mum to a care home very much against her wishes. It was either that or wait for a crisis to happen and I felt it was better for mum to be upset at me rather than sectioned or in hospital after an accident. As it was though she thought I'd come to take her home every time she saw me, the person she blamed was my 'nasty boyfriend'. She also claimed he had stolen all her money. I don't have a 'nasty boyfriend' just a rather nice husband, and he had nothing to do with the decision to move mum and certainly hadn't stolen her money.
You've had some great advice so far, I think changing the subject using compassionate communication is a good thing to do, though I found it tricky when mum was very focused on wanting to leave or on the nasty boyfriend. In the end I could spot when she was starting on another obsession, for instance that nasty boyfriend was my lovely and long dead uncle Eric, and quickly stop reminiscing about him and change the subject.
I also think not visiting for a week or two may help. In pre-covid times I made sure I visited when there was an activity going on, so I could help her join in. I also slipped away when she went to the loo or to lunch rather than saying goodbye.
This forum is such a useful place, using the search bar at the top will bring up similar threads that may be of interest. Some will be old, and the posters not around any more, but they'll still have good ideas on coping with this very tricky situation.