I Don't like Pizza

My mother-in-law is apparently going deaf--except when she can hear. My husband doesn't know if it's an attention thing or if his mother really has phases of hearing loss. She can hear any sentence with the word "sugar" in it. I am currently going through a pound of sugar every 4 or 5 days; my husband says it's the children, too--I think not. I ask my mother-in-law if she would like a slice of cheesecake. She replies she doesn't like pizza. I make the request more loudly and she says,
"Oh, yes, I'll have some cheesecake."

I don't know if I resent my mother-in-law growing old and her unawareness of her age or the fact I am suspicious that she knows she is being selfish at times and still chooses to be that way. The matriarch doesn't say "thank you" which means she takes things people do for her for granted completely. But I could be wrong and she may be completely unaware that some one has helped her and is oblivious to a standard of decorum. Do the old know they are solipsists? Are all old people this way? Do we as a community withdraw from the old or do they withdraw from us? The matriarch sits in her room and expects phone calls and invitations and me to go upstairs to chat with her. She makes no effort to come down. So, it this old age or her nature? And, what can I do about it when I have already taken her to senior centres and churches and the matriarch does not want to participate?

I know the matriarch doesn't like pizza; she has no teeth and cannot eat it. I don't have to be told.