There are quite a few medical conditions in which it is impossible to make it not hurt.

Ok. Even if we hold that ridiculous assumption true… so what? Let’s say grandma is explicitly suffering because others are failing her?

Your proposed thesis still suggests she does not have justification for choosing death. What does she still owe us.

I think you pivoted to another argument. Better would have been if you had started with that argument. Instead you asked what is grandma good for?