I'm going to ignore my ill great-grandma
Why would you do that to your great-grandma? She is family.
I don't like her and that won't change just because she is ill.
It's okay not to like family members. It is also okay to not be hypercritical about change, even though they are sick.
I can do it to anyone I want. She was mean to me before.
I suppose you have your justifications for why you are going to act the way you want to be. I will not judge your actions because I think people should get what they deserve. But I feel that it's important for the soul to learn how to love and to forgive, but that's up to you.