Loss of a parent

My mom died yesterday from alcohol the doctors took 10 liters from her body but the toxic was spreading all over and in her brain. She left behid two daughters and four grandkids. I havent talked to my mom in two years because of the drinking. I feel like its my fault maybe if I would have called her time to time she still would be alive today. My sister saw my mom die I wasnt in the room. I feel so guilty for that my sister has to live with that moment for the rest of her life. I want to tell my mom that I am sorry and I love her. I miss her voice her hugs everything. How do people cope with lossing someone like your mom or dad? I want her to come back to us