My grandmother has Alzheimers

My grandmother and grandfather we're always a big part of my life. I went to their house every weekend with my mother and brother. I remember so much happiness in that house, laughing with my family, laughing with my grandma and grandpa and just having so much fun. My grandfather died on my birthday in 2003. He was my best friend and I miss him and think about him everyday. My grandmother began I would say giving up after he died, and slowly we noticed she was slipping away and forgetting things. My grandmother was diagnosed with Alzhemiers a few years ago. It was easy in the beginning she didn't forget that much, she was still herself. Now... she doesn't remember much of anything. I get so sad walking into that house seeing how she is, not remembering much of anything, none of the happy memories that we use to have. It's so dark in that house, it just lingers with sadness now. You walk in and you can't help but get sad. No one wants to see someone they love go through this. She still remembers me but barely. Some days she thinks that I'm my mother when she was a young girl, and sometimes she knows exactly who I am and can remember everything we've talked about, and then sometimes she doesn't even know who I am and ask's my mother who the little girl is (which I'm 17 but little to her). I get scared that she's going to die, and I'm going to lose her, but then I think, I really have already lost her. She's not the person she used to be. She still thinks my grandpa and her mom are alive, and it breaks my heart when she thinks they've lefter her and ran away.... It kills me to have to watch her sob after my mom explains that they are gone and have been gone for some time and watch her whisper no one ever told me.... and she had been there for both. I'm scared that this is going to happen to my mother, I'm so terrified that she won't remember me when I walk into her house with my daughter. I'm so terrified of losing everyone.