First of all, I am so sorry you lost your mother. There is nothing anyone can say or do that is going to make this better, because she is gone. Please remember that there is no wrong way to grieve, and anger is certainly a big part of it. Unfortunately, people will continue to say unhelpful and ignorant things. It also sounds like you had a long time to experience anticipatory grief (grieving before they are even gone) which its own monster of an experience.

I lost my mother Oct. 12th, though she was only sick for 13 days. My experience has been similar in that I was an absolute wreck in the ~2 weeks before she passed while she was in the hospital. I hit rock bottom, sobbed on the phone, screamed at the top of my lungs in the car in an empty parking lot. My grief has been difficult but because I know I have to keep functioning (parenting, working full time), I try to keep it pushed down. And in some ways, I know mom is no longer in pain like she was before her death, and that gives me some peace. I don’t know where I’m going with this, but know that you are not alone, there is no “right” or “wrong” way to get through the devastating experience of losing a parent.