I started self harming when I was 14, for various reasons.
Sometimes its a cry for attention, sometimes its just another way of dealing, its certainly NOT ideal, but it did help me cope with the very tough feelings I was having. I don't advocate it as a coping mechanism at all, but now I look back and understand why I did it.
Does she have a CPN, or access to someone with specific knowledge in the field of self harm? Most decent people don't try to make you stop cutting, they try to help you deal with how you feel, so you don't need to cut kwim?
I don't know how to say this, so please don't take it the wrong way. PLEASE make sure she takes care of her cuts, provide sterile dressings and antiseptic creams and such. Cuts can get infected, and properly dressed cuts scar so much less.
If she is ODing on paraceamol you need to keep an eye on her, very small amounts can cause liver damage, if it happens again and she takes more than 10/12 take her to A&E just to make sure she is ok.
I don't know what to say really. If you want more info please CAT me.
Oh and BUS message board (bodies under seige) can provide very useful, drama free advice to families of self harmers.