Please accept my condolences for your loss of your friend. Looks like a long depression killed her. It's very sad. Depression is a terrible disease. Don't blame yourself that you had lost your friend. Depression cannot be cured by words, they provide only temporary relief to the patient. Many patients refuse to go to the hospital, not taking depression seriously. Although treatment of the disease have a good doctor by applying medication. This is a terrible disease that can come back again and again, when it seems that its peak is already behind us. It is a pity that many people do not take it seriously. In my country depression do not recognize the disease.Relatives may even laugh at the sick man, saying, "It's you against idleness invent, pull yourself together" or the like. And that only worsen the situation. Man retreats into himself, and unfortunately can not get out. I wish you to accept the loss, let your memories remain fond memories of your friend.