
I felt so sad as I read your letter. I too have had anorexia for most of my life and have lost good friends to this disease. It has the highest death rate of any mental illness.
But please don't blame yourself for your friend's death. Once this disorder gets its grip, no one on earth can loosen it. I almost died twice despite all of the love my family & friends offered me. The only way out is when the victim finally gets so sick of being sick that they refuse to be a victim anymore. That's what i'm doing right now, trying to nourish my body and not overexercise. (we always hear about the benefits of exercise but rarely about the dangers of overdoing it.)
i hope you are not too sad yourself, and that you can take care of yourself while you mourn your friend. Please don't take the blame our on yourself in unhealthy ways!