You have to try to stay strong, and you have to immerse yourself in the facts about heroin addiction! You have to learn to be patient and you have to learn to be able to detach. I am right now thanking God that my granddaughter is at this minute detoxing in the spare bedroom. Life has slapped her upside the head too many times. She is the light in my life and the apple of my eye and I also believe that I am all that she really has.
Get the facts my young friend and as much education as you can, but also keep track of your own needs and your own life- if you aren't healthy you can't help her as much as it sounds like you want to.
And you have to be realistic and you have to be prepared for the worst and hope for the best for your friend.
Only because I am an old grandma and know this I will suggest that you pray for her and also pray for yourself to be the best friend that you can be.
She knows you care for her- it is obvious here... take care and if you need to chat I can listen. Best wishes for your friend...