As the previous poster indicated, you are to be commended for your dedication to the kids that you work with - God bless you!
If you feel that you are seriously challenged with this client, please, keep in mind that the clients are looking to the professionals for the help, techniques, and answers. Even if you feel that you don't know how to proceed from this point, do it and learn as much as you can from the experience and, under no circumstance, let your client even guess that you're feeling challenged. There isn't any "right" or "wrong" way to proceed with the exception of passing this girl off to someone you might feel is more "qualified" than yourself. You have developed a line of communication with this girl and she feels SAFE with you, for whatever reason - avoid trying to second-guess yourself and attempt to figure out why she's chosen you and do your level best to help her work through the immediate crisis. Don't believe that she isn't headed for a break of some sort - the longer an individual holds out in expressing the emotion, the more volatile their reactions will be once they start the process.
The danger that you're facing is one that all empathetic counselors have faced, at some point in their journey: connecting with the client on a personal, emotional level. Not to say that it's inappropriate to connect, but how deeply we connect determines our own level of frustration, etc. That's one of the reasons that it took a long time for me to assist in counseling victims of domestic violence and abuse - I was too raw, too angry, and took the clients' experiences way to personally.
This challenge is going to help you to continue to develop that agape love and learn how to maintain a safe distance. You have been a benefit to your client and you're having to help her cope with something that is probably beyond your personal experience. Yes, it's a horrible thing that was done to her, and there will be steps forward, many steps backward, and many steps to the side for this victim to evolve into a Survivor. It will likely take years for her to overcome the issues that she's facing, so allow yourself time, patience, and continued support of this client. If you continue with this line of work, this won't be the only gang-rape that you'll have to help someone through, unfortunately.
On an aside, if you DO intend to continue working with at-risk children, you may wish to enlist the aid of a counselor for your Self (Self = that Life's Spark that makes you unique). Nearly every counselor that I've met and/or worked with (including my own) began with at-risk children and becamed so burned out in such a short time that many of their clients were still in counseling when they decided to throw the towel in. Having your own individual counselor will help you enormously to cope with some of the things that you have been witness to and things that you have yet to experience. Each client is unique even though they might have similar textbook issues - some will tug at your very soul while others will provide a level of frustration that you have yet to experience. Find a good personal counslor, Sparque, and continue the Good Fight for the innocents!