I'm very sorry for what you are going through. Having no other family can only make it worse, I'm sure. Please feel free to lean on the people here at the library. They're all good people, who really care.

I know that when my wife's parents passed, being prepared for it helped her a lot. They went peacefully, several years apart, and were in the process of dying for many months, if not years, before hand. So we were mentally and, to some degree, emotionally prepared. Her father, in fact, was very similar to what you describe with your mother. He decided it was time to go, stopped eating and taking his meds, and just went, in his sleep, in a hospice.

There's nothing you can do to keep her here, so the only advice I can give is to try to reconcile it in your heart. It's not much, but believe me, you can get through it.