My heart goes out to you - I can see how exhausted you are and I have been there - my child was suicidal rather than violent but also very aggressive.
I want to say something different from other posters. I think it's both important and urgent.
Your child is not actually at rock bottom - yet. And while it feels like hell, there is absolutely the chance to turn this around. In fact you must act rapidly and decisively - and you will all feel immediate relief.
I think she is on the cusp of total burnout and the way for you all to survive is to lean into it and get support for where you are NOW- not where you hope to be, or where you thought you were before.
You are saying you thought she was "a little bit autistic". I conclude from this that she is intelligent, has been able to mask successfully in earlier life, has achieved in the ways you think are ok - school and hobbies - but now everything is breaking and she can't sustain it any more.
So is she in crisis? I say yes - AT THE START OF CRISIS. She is just going into a deep burnout which you will need to navigate.
She goes to activities and courses. She has not yet fallen out of those BUT she is struggling socially- so without immediate and urgent support it is another ticking bomb.
She is able to spend time outdoors and in nature with you at work.She actually comes with you to work. That is a good sign as there are things that regulate her and shows she is not actually in full PDA anxious fearful refusal of everything. Not yet.
She has been going to school until very recently it sounds like, though the placement is breaking down. Last Tuesday is nothing!! it's only a few days!! She is literally in the middle of realising she CANNOT COPE AT SCHOOL. She is terrified on some level that she willl continue to be forced to go there. She doesn't have the words or emotional understanding or interoception to advocate for herself. No wonder the violence is escalating. She has no other way to communicate.
She is 12 - has she just finished year 7? In a mainstream state school? Did she have a transition earlier this year into a new school? What was her behaviour like a year ago?
What demands are on her now? It feels from your post that her violence is triggered from what you see as ordinary everyday tasks and demands. This makes me think you haven't quite grasped the type and quality of help she needs, although you have fought super hard for help to the point where you are exhausted.
The violence seems to have escalated now and she is hugely dysregulated a lot of the time. She is seeing "ordinary life" as too much, now. This is a crucial turning point.
I don't want to scare you- but although she is violent, her life has not yet completely halted. In some ways, you ain't seen nothing yet. You have not yet seen her burn out completely.
Crisis action plan for yourself and her, right now.
- Accept, radically - the world as you knew is is GONE. You will not have 2 daughters nicely going to school and passing exams - not in the next 2 years at least - and your family and working life will be changing. You need to find out more about autism and burnout in girls - wherever you can, however you can. You must stop expecting that this is a blip and she can kind of keep going, things are about to stop and change. You are assuming she has capacity for quite a lot of normal life, when really she is almost totally depleted.
- Tell her - when she is calm - that you have now realised and you understand she cannot manage things. You promise you will, as of today, not make her do ANYTHING. And certainly nothing that makes her anxious, scared or angry. You know she has been trying hard and you understand that people haven't seen this and haven't helped her enough. It's ok for her to be angry and alarmed (though if she hurts you or her sister you will take yourselves out of the room, to a place to keep yourselves safe). You are on her side. You will not make her go to school, not now, not next term, not ever. There will be no punishments or sanctions or expectations for now - only understanding. None of it matters, only safety matters.
- Go completely, dramatically LOW DEMAND. Like, ZERO DEMAND. Demand so low you would not even think it is a demand. If that means she stays up all night and sleeps all day, spends 10 hours on YouTube, eats only beige food, doesn't leave the house, doesn't wash, then that might be where she is, for days, weeks or even months. Take as much off her as you can. Allow any and all special interests, in depth, for as long as she wants. Do not make her eat with the family, talk to anyone, deal with anything. DO NOT listen to the voice in your head that tells you boundaries are necessary and you are making a rod for your back, etc etc. That is bullshit. This is the only way.
- Co regulate with her in a PDA friendly way. For mine at this point, this looked like saying "i notice you're wriggling about, the door to the toilet is open and it's free right now". "Here's a drink of water on your bedside table". As yes, the burnout got so severe she couldn't even accept the demands of her own body. I was putting her pants and socks on for her. She was a super bright high achieving verbal "totally normal" child before burnout- their capacity needs to fluctuate down to almost nothing, to allow recovery.
- Does she have any ongoing suppoet already? Does she have an OT or speech and language therapist? Maybe get one - who understands that it will be incredibly slow progress and for months perhaps they will be just alongside her as she plays Dress to Impress or looks at pictures of horses, or whatever she is into. Then they can start understanding her world, helping her understand why things have felt so hard. But that is a while down the track.
- Chuck money at the problem, if you can. I know this is hard. But get private, sympathetic, OT/psychotherapy/SLT/ whatever you can find. Just one individual to take you through and help you, one person who can do the relational work with you and her. You might also need to stop work. I'm really sorry. There is no cheap way to retain normal life at this point.
- Let go of the hope that there will.be rescue from the system. "Putting her into care" is not easy, not simple, might not work the way you plan. It also puts you at the mercy of services which are not fit for purpose - camhs, social services, the LA. They have harmed you already and will all harm you further, your family will be fractured and both your daughters, and you, irreparably traumatised. Your younger daughter will either have survivor's guilt or be taken from you. I know it feels like the only way out, but there's another way.
In summary...
There is time to heal your family. You must stop. You must pause, stop pushing yourself, stop pushing her. Let her be in burnout, let yourself go down into it with her, and let yourselves all recover.
The thought of you pushing yourself hard at your desk, sore, angry and hurt, with nobody taking care of you, trying to collate all the information, trying to order and control - that makes me sympathise with you, so much. But that rigidity in you is part of the family dynamic too - you must try to let go of control. It will come back, renewed, with your energy, fresh and calm, I promise you.
The old life is dead. The violence will ease off as the pressure on her eases off.
I wish you so much luck and send as much care as I can xxx