It's really hard to lose someone important to you. I'm so sorry you have to go through this. :-(

I also know that it doesn't matter what I or anyone else says you will still greive the loss but please believe that there is a waaay better friend out there for you. Someone who can support you regardless of your siuation. The only other thing I would suggest is that you consider your friend's criticism and look at yourself and honestly see if you could do anything different in the future. If you feel like you did your best then thats fine. You'll find someone worth your time and friendship! Keep your head up!