This is quite an emotional post. Personally, as a friend, I would encourage your friend to report this person to the police. She may not be the first or last victim. On top of this, I would encourage you to advise your friend to seek specialist help, such as counselling. I cannot stress the benefits of this enough, particularly for her situation. Antidepressants cannot help her with the trauma that she has experienced, only with the neurological basis of depression.
As a friend, you need to be supportive. To be honest, the trauma of the experience will never end, and you have to be prepared to deal with that. Though your friend may be reluctant to go to the police, please, PLEASE remind her that other girls WILL be at risk if this is not reported! And counselling is not like it is in the films, it had helped so many people, it is nothing to be ashamed of, and it is very important that she seeks the best help available.
Best of luck, A x