I'm staying with my grandmother who has Alzheimer's

My 88 year old grandma has Alzheimer's. About a year ago my family moved her into a retirement home. Shortly after, being unsatisfied with the care she was getting, my mom quit her job and moved my grandma in with her and my dad, so she could care for her full time. My parents are on a much needed vacation and so I'm staying with my grandma while they're away. I thought the roughest part would be being away from my husband and dogs for so long. But I was wrong. I see my grandma about once a week. But I've never spent this much constant time around her since it started getting worse. So now I'm seeing her episodes more frequently than before. I knew she had them because my mom would tell me about them. One day she thought she still lived in a town she hadn't lived in for over 30 years. Another day she was talking to my mom, and kept confusing her with me. She keeps talking about where she's going to go live next, and I have to keep telling her that she lives with my parents now and isn't going anywhere. She still knows who I am when she sees me, so I still have that. But she isn't the same woman I knew growing up, or at least she isn't most of the time. What really hit hard tonight, before she went to bed, was when she looked at me and smiled and said "I really don't know where I am right now." She can't remember that she lives with my parents or that she's even in their house. These are just a few examples of her episodes.
It's been a rough week. And I'm glad my parents are coming back tomorrow. But my heart hurts for my mom, who has to see her mother like this everyday. If just a short time is bringing me to tears, I can only imagine my mom's pain. But she tells me that she's happy she gets to spend every day with her mother, lucid moments or not, and that we have to take advantage of what time we're given.
So hug your family close. Or don't. I just needed to get my sadness out to some strangers. Go back to looking at dog videos. It's what I'm about to do.