Can sometimes say a few words and is unable to open her eyes? She can hear. She has had dementia for going on 5 years. It makes me sad to see and I also wonder if she feels pain? If she is scared, or if it is just me who is scared for her if she feels pain. All these questions arise in my thoughts.
Who is her primary caregiver? Who has her medical POA?
How old is GM?
Is she on Hospice care?
Other than your natural concern, is there any indication that she is in pain? Does she grimace or moan? When she says a few words what are they about? Is someone re-positioning her (to avoid bed sores) every couple of hours? How does she react to that?
What is the nature of your role in her life? Visit every couple of weeks? Spend time with her daily? Are one of her caregivers?
When my grandmother (in another state) was bedridden at the end of her life her oldest daughter spent time with her at the nursing home daily. She said sometimes Gram mumbled or smiled or laughed, and she seemed to be remembering happy times, mentioning the names of her children now and then. My aunt concluded that maybe she wasn't as miserable as we would assume. You may think you'd be scared in your grandma's situation, but it is hard to know what she is really experiencing.
The fact that she can hear is positive. When you sit with her you can say soothing or encouraging things, whether she indicates understanding you or not. "Grandma, you did such a great job of raising your three daughters. They are all independent, productive, and happy women. Millie had a hard time when her husband died, but she has grown and is strong and happy now. My mom Mary has been an awesome mom just like she saw you being, and she is happy in her career. Carol is enjoying her empty nest. She is coming to see you tomorrow." "Grandma, it is a beautiful day today. While I was driving here today the trees were glorious in fall colors. I hope you remember all the autumns you have seen those wonderful colors, and that the memories make you happy." "I've brought some music that was popular when you were in your early twenties. I'll put it on the play now."
In other words, focus on contributing to her comfort or happiness in any way you can.
Tell us more about your grandma's situation. Others may have some specific suggestions.
One of the users of this site cared for her mom in a bed bound state for, I think, about ten years.