Tough situation. Sorry several of you have gone through tough situations. This reminds me of when we put mom in memory care. We would ask her in front of her doctor, or a care facility director if she was ready to move out of her house and she'd say no lucidly enough. I talked to a lawyer and he said it was going to be a tough fight even though I had a signed medical POA from her. As it went I checked her into a memory care facility under the guise of her needing care for wound care after minor surgery, and although she was agitated a few times in the first few weeks, she quickly accepted this was her home and fell into a routine.
Sorry if that is not specifically helpful to the OP, but, getting someone help when they tell you they are fine is tough.