I sent her the following response, based upon what I learned when my mother and aunt had Alzheimer’s.
Yes, it is sad to see our parents go downhill with illness and memory loss. I eventually realized I was bringing Mother joy even with she didn’t fully respond.
Someone once asked my granddaughter Kara, about 7 yrs. old then, “Why do you visit your great grandma when she doesn’t know you?” The little girl (wise beyond her years) replied, “Because it makes her happy.”
So somewhere, beneath your mom’s seemingly unresponsiveness, your visits “make her happy.”