We live in the UK, I'm 25, my 'little' sister (LS) that this post is about is almost 15 and 5'8, my younger brother (YB) is 13 and my youngest sister (YS) is 12. All three have the same Dad, my Step-Dad who divorced our Mum about 9 years ago.
When LS was about 10, she was diagnosed as having autism after years of campaigning by our Mum.
When she was younger her behaviour wasn't as excessive, she would pour drinks on our heads, push us, hit us, break our and her things, but Mum and my Step-Dad could handle her, she'd get things taken off her, grounded, but she never seemed to care.
Fast forward to when she was about 12 and her behaviour is escalating.
She's left many scars on our LB, she hits our YS for looking at her... But she's perfect at school. At home someone touches her coat so she has a melt down and tries to strangle my dog, but when other people are around she can control it, which is what I'm unsure about.
She ends up living with her Dad, but still comes to the house and terrorises us "it smells like wee in here" because we have pets, saying YS stinks, starts trashing the house, me and Mum get all the pets on the other two and lock ourselves on the conservatory so she can't hurt us, house get trashed, things we've made or expensive things we care about are trashed, she deliberately goes for these things.
She finally leaves, she walks off all the time and you can't restrain her. When she was younger she would run off whenever she was upset regardless of where we were and police had been called to make sure she was safe.
She has a fall out with Dad and runs away from his house and wants to come to Mum's, we say no as LB is terrified of her and is having a negative effect on his mental health.
She smashes the window on our front door and runs off.
Last year Step Dad gets in a bad road accident, luckily survived, but is now paralysed from his chest down, luckily he has use of his arms and hands and can breathe by himself, but still very sick and a lot of healing to do.
While he was in hospital LS lived with his parents and after a few months her behaviour picked up for them.
Now.
She's back living with Dad, but he has carers, so any conflict or violence in the house and he will lose his carers, which he needs to get out of bed, to change his catheter, to set his machines and to move him so help his pressure sores.
She's not been to school for over 20 days so we have the threat of court proceedings, a lot of social workers and attendance officers coming over, but she barricades herself in her room so they can't see/speak to her.
Mum went over about two weeks ago to try and speak to her to get her to go to school and LS pulls a knife on Mum.
Mum just leaves and let's LS calm down.
Last night LS decided she was too hot, despite wearing a dressing gown and being under blankets, so asks for central heating to be turned down, Step Dad is cold and needs the heat and so she is told no.
She goes upstairs and starts slamming and hitting the doors, trying to break the walls, etc.
So Step Dad phones his Dad, and LS pulls a knife on him then starts smashing up her room... While the other two were there spending the night.
Police are phoned and after about an hour they haven't shown up and she manages to run off.
Police are phoned again to say she's run off and they get to the house straight away, after about half an hour she's found and they follow her as she walks back onto the house, the second the police leave she runs off again, so police try to get her back into the house and she's completely ignoring them.
When she does go back into the house she barricades herself in her room and starts smashing more things.
After speaking to the door for a while police barge door down and she's very aggressive to the police to the point they have to phone their Sargent.
So she goes downstairs and starts threatening to turn of Step Dad's machines, threatening the other two, laughing at everything.
Step Dad doesn't feel safe and has asked her to not stay at his house, she refuses to go to Mum's or Grandparents, but social services can't be contacted until Monday.
The Sargent tries with her for about half an hour to talk to LS, but LS is being awful.
Unfortunately another incident comes in and as she's now in the house, they leave her.
Cahms won't work with her and have removed her from their books.
Team around the family want to help, but she won't accept it.
Social Services are now involved, but I'm scared if she's taken somewhere else she could seriously injure someone.
Mum is concerned LS, as well as having autistic traits and OCD, could be a socio/psychopath.
What can we do?
Mum is completely devastated, she's done everything she can and doesn't want to give her over to social services, but we're out of options.
There are no child mental health wards, police won't detain a 14 year old with mental health problems, she can't stay with her Dad anymore.
What on earth can we or anyone do?