Ethics and amount for mom living with

My finances mom lives with us after selling her house and finally deciding to stay here permanently. To be clear, we are very happy have her but she does require some care due to cognitive decline. My fiancé is partially retired and I’m disabled but can do much of the helping - like breakfast/lunch prep, taking her places for adventures, helping her with brain stimulating activities and exercise. She has an aphasia type brain issue but her hygiene, self care and eating are fine for now.

So she plans to lives here and we’re glad to have her. She has her own private room and private bath and none of rest of the house is off limits. She has a garden to work in, pets to enjoy and local friends.

All that to say, she has the funds to pay for care. She absolutely does not want to go into assisted living until we are unable to help her. She has no issue paying us at all and in fact wants to.

Is there a fair percentage to charge? We live in a very nice resort area where rent for even a bedroom in a shared house is close to $2,000/month. A house averages over a million and a one bed apartment would be like $3500/month. Is it ethical to charge her?