I'm so sorry. We're dealing with this with my grandmother. We've chosen an assisted living facility for her and hope to move her in soon. It's been so much on my mom, so I'm glad that her burden will be lifted.
Also, I will echo the comments of getting yourself support. To have the capacity to enjoy, support, and love her you will need breaks. Sometimes because you'll be tired and sometimes because you'll be sad.
It's also OK to have moments when you're scared for your own future. I know I am and my mom is after going through this with her dad. That doesn't make you selfish or unloving.