Many years ago I used to be a cutter. I can’t say what your daughter is going through, but I can tell you from my experience, it was a way to control my out of control anxiety. The cutting is a symptom of Whatever illness is plaguing her. I didn’t try to hide mine either because even though I wouldn’t have admitted it at the time I was terrified and screaming for help. Maybe the therapist she saw wasn’t the right one for her. Try someone else and get a recommendation from a pediatrician as to who is good with teens. Or maybe she would do better with a group therapy where she can talk to other teens instead of one on one with an adult which can be intimidating. Don’t give up! Good luck!