We went through this with my m-i-l 2 years ago. If she had been to a doctor (which she has refused to do for 50 years) she most certainly would have been dx'd with dementia when she reached our house in April.

I spent most of 2 months feeding her heathy food, and she had started knitting and crocheting again, reading, walking outside, and could hold a conversation. You'd never have guessed she was so bad 2 months earlier.

Then she moved into her own place and refused to eat well or cook. She just drank coffee and ate sweets and ice cream from the store across the street. She deteriorated rapidly and is now in a locked ward for dementia wanderers. We could not force her to eat, it was her choice.

She was fully aware of the difference it made to her well being, but still made the choice to not eat well.

I just don't understand not working for a good quality of life, especially when there's family to help you.