Why does mom eat sporadically?

My mom had a bad stroke in April and the doctors said she would make it three weeks. She is on month four. She can’t leave bed and needs to be fed purée food. It’s extremely hard to watch. I love her so much and keep thinking she will get better. She has her good days - little bit of talking, drinking, and a few bites of food and then she has her bad days where she goes three days without eating; although she drinks well. It’s a pattern. She will go a few days without eating and then the fourth day she eats 25% of one meal.
She is able to muster the strength to tell me she loves me most days. And I do get to visit her and hold her hand. I feel like she knows I’m there but she just stares at tv for most of time or sleeps.
Hospice nurse said she is entering the last couple months. I’m confused by this. What if she bounces back? How long do I have with her? Sometimes she’s able to talk and eat well. Hope bubbles up inside me that she will bounce back. Everyone tells me this is not possible. They also told she wouldn’t make it past three weeks.
I have put this all in Gods hands and know she will leave us when it is her time.

I feel guilty bc I live 1500 miles away. I will stay a week with her, fly home for a few days to attend to work and then fly back to spend another week.
My dad is in same nursing home and spends everyday sitting by her side.
The whole thing is a tough process to watch.
I’m very grateful to spend this time with her. Sorry if this is a ramble. I love her so much and it’s so hard to watch.