Now what?

My mother is getting on in age - 89 this year - and while we're concerned about her physical limitations sometimes, its her mental disposition that has me worried lately.  Recently I visited her, and I wasn't in the door 5 minutes before she told me to come into the living room so she could talk to me.  To make a long story short, she laid into me.  She said I yelled at her in a previous phone conversation, called her a "bore" and said I told her "I was sick of hearing" about her eye troubles. When I told her I did not say those things, she said I was either a liar or losing more than my hearing.  She said she was "quoting me" which could not have been so.  When I reminded her of the facts  - phone calls, letters, taking her for errands, bringing her lunch, cleaning, bringing her things she needs - she sneered and said "Oh yes, you are the perfect mother".  She had a lot of negatives to say about my sister Alene, too.  She told me she's been having bad dreams - could she have dreamt I said something?

I had spoken to her a couple of times that week and she seemed perfectly reasonable.  She was insistent that I had done wrong.  So I told her I would fix her a good lunch, then leave. The rest of the "visit" was awkward.  She asked me if I wanted to "come look at this quilt you're not interested in" - again, something I never said.  It was hard to turn the other cheek, but I did the best I could.  She wouldn't allow me to clean or do anything to help her around the house or take her anywhere, so after lunch I hugged her and said goodbye.  Then I went directly to meet my friend Carol at Saddlehorn a little earlier than we had planned. I'm not sure what the next step is in ensuring she has safe and happy golden years.  Now I am a little more worried about the possibility that she has some dementia.  What to do?