Memory Care would be considered the same as a nursing home.  As long as it is medically necessary for her to be there, you can deduct all of the cost.

"You can include in medical expenses the cost of medical care in a nursing home, home for the aged, or similar institution, for yourself, your spouse, or your dependents. This includes the cost of meals and lodging in the home if a principal reason for being there is to get medical care.

Don't include the cost of meals and lodging if the reason for being in the home is personal. You can, however, include in medical expenses the part of the cost that is for medical or nursing care." https://www.irs.gov/publications/p502#en_US_2018_publink1000178988