My mother-in-law has no teeth. What can we feed her that she'll like and eat?

My mother in law has no teeth whatsoever in her mouth. She barely brushed what teeth she had before her numerous health issues began to deteriorate. Her teeth were brittle and just broke off at the crown. Her gums are black and her gums have started growing over the roots of her teeth. She has me fix regular food for her, but she doesn't eat it because she can't chew it. I even grind and puree it and she still doesn't eat it. She wastes so much food, that we don't know what to fix for her for nutritional value. She eats 1 1/2 to 2 gallons of ice cream a week. That is basically what she lives on. She is homebound and bedridden, (her choice). We have brought in a nurtritionalist to over suggestions, and I've tried them and she doesn't want any of it. We don't know what to feed her anymore. She can't even chew cherries, grapes, or even watermelon, she claims there to hard. Any suggestions?