The long good-bye

I went home for a visit a week or so ago. Home ? It's not my home anymore. Its just the place I grew up, so many long, hard days ago. I want it to be different, but it not going to change for the better now.
My mom has Alzheimer's disease. Its such a hard pill to swallow. We've been calling it dementia for a few years now, the result of a fall on the ice. She seemed like she was getting better, stronger for a while after rehab. , but things never really came back to normal. Now it's Alzheimer's. Its called the long good-bye for a good reason. Pieces of your childhood slowly disappear , as though they never happened at all. Mom's childhood memories seem to be there and she clings to them for proof that she doesn't have "that thing". That thing that she can't remember what its called, but she doesnt have it. She tells me over and over. That's the recurring theme of my visit with her. Over and over, the same stories with the same inflection, the same surprise when I say that I've heard them already.
I know in my head that she she has Alzheimer's, but some part of me doesnt want to accept it. My sisters and I keep getting hurt by the stories she tells. Her brain has made up new stories as though they were the truth and now these are told over and over. We try to rationalize with her, to show her how the stories can't be true, but somehow that information does not enter her brain. We get mad and indignant and say "how dare she say that" and "that's just not true", but we are still learning that its Alzheimer's speaking and not our mother.