How can i accept that my best friend died? already!!!?

My best friend died when I was 11 years old. I am now 17 every time life gets overwhelming I always go back to if she were here everything in my life would be different. I always blame her death on all my problems. Some times i have dreams of here telling me shes not dead. becuase ive never actually seen her dead she got cremated before the funeral so i never got any real closure in proving that she no longer here how in the world im i still going through this 6 years later i just want to move on with my life but it truly the tuffest thing i ever had to deal with it like a life long battle with myself