My Mother-in-law Is In Hospice And Has Not Had Food

My Mother-in-law is in hospice and has not had food for 19 days and just sponges in her mouth dipped in water for 3 days. She is a skeleton with skin on it! Probably 55 lbs if that. Tonight I thought we saw traces of blood in her mouth and her tongue looked very dark. No mottling or breathing issues. How long can she go on? It is so hard to see her waste away.