How to deal with my mom that is now in heaven?

Last year, in June my mom didn't feel good. She drove to the doctors, and they took tests and she found out that she had leukemia. She got rushed to the hospital and she was there for a month then she came back home, because the medication made her better. But this year after all the bone marrows, medicine, stem-cell, and a leukocyte.This year went to the hspital again and the doctors gave her medicine. But she wasn't getting any better. And last night, my dad told me "mom will be going to heaven tonight" and I was so confused, I ran to my room and started crying. She was my best friend and she had a good additude. She didn't sit in the hospital asking God why her she went through it, and now I think she died...I'm not sure if she died because I'm still confused because I didn't understand what my dad was telling me...Please give me advice on how to deal with it thanks! :)