I'm so sorry about your Grandmother.
My dad passed away a 2 years ago. His last week, he slept most of the time. The last 2 days he was not awake at all, although at the very end I think he knew we were there. I was fortunate that he lived in the same town I did, and I could be there every day.
I guess what I'm saying is, since you don't have that opportunity, I would not try to wait until the very "last days" if you want to still be there when she is awake and you can talk to her.
The Hospice nurse told us (and this was true for my dad) that about 5-7 days before they pass away, you'll start to notice their extremities will start to turn a bluish gray, and they will eat less and start to sleep more and more.
Good luck. I hope you get there when you need to.