Dealing with a bereavement?

My nan died two weeks ago tomorrow and l have been devastated. This is the first death in my family that l have experienced. I am 37 with 5 children and l feel like l am going mad. She was 83 and died as a rsult of neglect by her son. we were only told she was dead the next day. I have so many questions and regrets going round in my head. My children are devastated l am trying my best to comfort them but l don't understand the total waste of life myself. She could have easily seen 90 but her life was cut short. People tell us she had a good innings and we should be grateful but she died alone before her time. Has anyone any advice.