I had a young friend who shared with me the problem that she had beginning when she was 15 years old. She used to cut herself, too. She told me that she had learned to shut down her feelings to the point she felt emotionless, regardless of what happened. She was pretty low in the self-esteem area, but she covered it up well.
She had a GOOD HOME LIFE… She said when she cut herself it was a ‘relief’ to feel the pain and the fright because at least it was FEELING something.
Her mother found out and insisted that Lacy go to therapy… which she did for several months. She did not have a drug problem, or one with alcohol. Lacy was otherwise a very likeable, delightful. intelligent young person who got on better with adults than her peers. She would have been MUCH better off with home schooling. She finished HS online, and then enjoyed taking some college classes of her choosing.
She was grateful for the therapy that her mother insisted upon. So, please do not give up. This is a problem that CAN be overcome. Good luck to you and your daughter.