Coming from a person who use to do this...
I finally over came my self-harming when I got control of my emotions. I use to cut myself because I could not control my emotions so instead of having the emotional pain I would draw my attention to physical pain as I could handle that pain so much better. People need to realize that's why people cut themselves... Its not for attention and its not to necessarily hurt themselves, its to distract them from their own emotions. I did this when I was 16 and my mother had me go to a doctor to "talk". I sat in that room for 45 minutes and didn't say a word. I told my mother talking to someone that I don't know will not help me. You are paying him to be a "friend". She only sent me there one more time before she realized shes wasting her money on something that is pointless. Some people, however, get great help from talking. I did not.
Tell her to try to tough it out. Next time she gets in that mood where she can't handle her emotional pain, tell her to play a sad song or a angry song and cry it all out. Once she learns to get past the mountain, everything is a simple way down. She will be proud the first time she over comes it and it will inspire her to continue to keep over coming this!