What are some signs that end of life is near?

My grandmother's health and mental status had been declining to a point that we decided (me and her together) that it was time to move to a nursing home as I cannot provide the care she needs. We are waiting for her acceptance to the home and for her insurance to come through, so in the mean time she is still at her home and I am there almost ever day of the week. The days I am not there to visit (for around 4-5 hours) my husband goes.
She seemed to be doing SO much better last week! She was very talkative, walking around with her walker faster than ever, finishing up several projects and books, eating full meals ect.
On Saturday she called asking for some protean shakes as she was feeling very weak and couldn't even open her dog food. During my visit today I noticed that she only ate about 1/4 of her dinner, there were no crumbs on the counter so I know she didn't eat lunch or breakfast, I could tell the dogs hadn't been fed or let outside. Her breathing was labored, and she kept dropping her head and closing her eyes. Her lips were tinted a much darker color, and her voice was weak.
Her conversation was gone today as well. She said very little as we sat at the table together.
We have a doctor appointment that I set today after about twenty minuets of being there, the soonest they could get her in is the 24th and she refused the emergency room for a quick check up.
She hasn't been well for over a year now, and it seems like this is a very very fast and sudden decline. I had an aching feeling that she just will not be around much longer.
I am hoping that the nursing home will be in contact this week with a move in date, so that I know she will be monitored 24/7 with daily visits from me and my husband still.

But tonight I just feel lost and worried for her.