waterfall

My mom has Alzheimer's. She is 76. Every time we visit her, she is getting worse and worse. She repeats telling the same story over and over again (every hour), forgets things constantly, and pretty much can't support herself in life. Luckily, my dad, 79, is still healthy and alright. He is the man who takes care of her and plus everything in house. They live in Vancouver, Canada and we live in USA, so we only can visit them couple times a year. My mom doesn't admit she has this problem and she always blames my dad if something goes wrong. My dad is kind and does not want to argue with her. She is always yelling at my dad for not doing this and that at home. She doesn't know how to turn on the TV or how to change channels and she will blame it on my dad for not setting up the TV right. I have tried to explain to her not to do something like that to dad, but she is a very stubborn person and has her own mind. Sometime when I see this happens, I just can't stand her and will get mad. What should I do in this situation? Please help.