Unsure on how to feel about my grandfather's death?

My grandpa was an abuser/alcoholic for most of his life, and put my mom and her brothers through hell in the past. Now he is on his death bed, and has been for several months. The way my mom is behaving is astonishing me, she has been visiting him every few weeks (we live very far away from him too), and trying to help out in any way she can. I'm having a very difficult time trying to figure out how I should be feeling about this situation. I don't have a lot of respect for him, and we were never close. I can't understand my moms behavior either...I can't forgive him and the horrible things he did, and they were not even done to me. Do you guys think someone can truly 'change'? Do you think my mom is expecting an apology from him that she isn't going to get? Any advice or thoughts please.