15 Year old DD. HELP!!!!!

[FramptonRose]

I just wondered if anyone has any tips to help me.

15 year old DD is currently being assessed, I actually think she shows signs of Asperges although I don't think that term is used now but school and I both agree we feel she is on the spectrum.
Part of that means she is very rigid in her thinking and I don't seem to be able to get through to her in terms of behaviour, she is a good kid amd very polite but if she does do something wrong, when you try and talk to her about it she will just shut down as she cannot accept any responsibility whatsoever! She can also be incredibly childish.

Her fighting with my youngest ds who is 9 has become a real issue, 9 year old is a pain in the bum, granted, but she will constantly engage in arguments with him, if he says the sun set is at 4pm she will argue with him, gets her phone out to prove him wrong which leads onto more arguing.
This example sounds like normal sibling silliness but honestly it's all day everyday and it is driving us mad!
I have two other children in the middle and there are no issues with them other than the normal odd argument with eachother.

Has anyone got any tips to try and stop the constant fighting.

I’m not sure what it is you are asking, tips for helping with what?

Sorry probably didn't put it word my post well.
It is the constant fighting between my.eldest and youngest but just wanted to explain my eldest does have some difficulties with processing so anyone that may have a similar situation that may have a few tips.

My eldest sounds a bit like your DD especially in terms of taking responsibility and winds up the youngest a lot just now. I am trying to spend a bit more time with eldest on his own as think he wants more attention and time without the youngest (they do a lot together so they don't get much space/alone time).

I would seperate them for 30 minutes each and every time it starts.. in seperate rooms with the door shut.. no discussion…
They will soon learn not to bicker!

You could try a chat with both of them when no one is actually arguing

look you two, you are both creating a lot of agro in this house with all your nit picking and arguing…assuming both of them try to jump in and argue with you at this point..hold your hand up and go ….exactly. This is my point..neither of you are prepared to be curious about each others point of view, give the benefit of the doubt or quite frankly be friendly..so I have decided that we are going to have a new regime.
Any arguing, raised voices or unfriendly comments then you will both leave the room. Im not interested in who is right, wrong, said it first, looked like a smurf, whatever…I just dont want to hear it. If we are in the car I will stop it as soon as it is safe and you will both get out of the car until you can zip it around each other. This is not up for discussion, it is my decision and final. Do you both understand..

and then stick to it. You might see some changes in about a week.