I'm so sorry that this happened. A friend of mine has an aunt who has Alzheimers, when he comes up to see me, we take his aunt out to eat, or over to our friends house just for a change of pace for her. I don't know her long, but I enjoy the time that I spend with her, and it leaves me with a good feeling of making at least one day different for her.
Forget about R right now, and just sit with the good feeling that you had today, and the wonderful time that you spent with your mother and your daughter.
(Hugs)