SC you've done nothing bad.
I am a well nown Mimsnetter, i changed my name just for this- I hope you don't mind. If you want to check who I am I am happy to tell you in response to a cat message, just not in public if that is alright.
I have a history of self harm, culminating when I was about 19 with pouring boiling water over my arm until it blistered badly. I've also cut myself inthe past, and it was alongside an eating disorder.
Why did I do it? because everything at the time semed so bad and I needed to feel some sense of control I suppose. I felt severe guilt for lots of things that ahd never been anything I was responsible for, but of course teenagers aren't that rational. When I hurt myself, it felt a small bit like a pennance, but also I felt a tangible sense of that guilt lifting for a while. It was also a cry for help- I thought if someone would see, they'd realise how bad things were for me (nobody ever did but that was a LONg time ago).
I hope it reassures you to know that it passed. Occasionally when things are very traumatic I still feel a little like it, but I haven't acted on that in over a decade. As I matured enough to be able to take proper control of my life, and I learned how to affect positive change myself, the lack of control changed with it. The eating disorders still raise their head very occasionally, but are mostly under control.
Please don't clame yourself for what is happening to your daughter. Its a reaction to beinga teenager I expect. As long as you make yourself available for talking, and can find a way to help her learn to take control in more appropriate ways, then youa re doinga ll you can. Having ehr see a Psychiatric Nurse was the best thing of all- exactly what is needed I feel.
As for the little ones and social services, your daughter does need to learn that she cant traumatise them this way. I have a disabled son who is violrent on front of his siblings,a nd I have also ahd SS involvement. In no way were they accusatory to me: they ahve seen it all a thousand times, and will just give the advice they can.
I wish you all luck.