Grandma's actions don't occur in a vacuum.


Grandma moving in will affect everyone, not just mother and father.


So the OP is involved whether they like it or not, and whether members here agree or not.


I agree that a family meeting is called for, maybe if father hears more than one voice he'll be open to hearing some sort of reason.


Besides, she's able bodied and basically lives down the street, so no need to buy a whole new house to accommodate her whims.