Being as I have been in a abusive relationship and looked at it from every angle, I honestly believe that you should send that in for to her parents or close friends but leave ur address off of it. I agree that nothing you say or do can make the poor girl change her mind, but I you can warn the loved ones in her life maybe they won't dismiss a black on or multiple bruises on "the door" like so many of mine did. My own mother never caught on to the abuse while I lived with her. I had multiple black eyes, bruises all over, bruises around my neck constantly and 2 torn rotator cuffs and the people I was closest with never even knew. I look back and think if maybe one of them had come forward and said "I can physically see what he's done to you and you don't have to live like this" maybe I wouldn't have endured so much violence and hate.
So that being said, PLEASE PLEASE PLEASE do something. I don't know how anyone can sit back and say do nothing for this girl. I might even send her a small note that says something like I'm here if you need help. You might just be saving someones life and to me thats not considered butting in. And if it all goes to hell and you get nothing accomplished, then at least you can say you tried and not feel guilty. Good luck.