I asked her to go out with her dad today with my other kids as I just wanted to be in this house alone and not have to worry about dealing with her she's refused to go
This is awful.
You cannot ask your child to leave their own home for the day because you can’t be bothered ‘dealing with her’.
That’s awful and I would never say that to my child.
It’s no wonder why you two have issues.
If you want time alone then go into your bedroom.
Obviously her having rubbish in her room is not good.
My DD is similar and I regularly tell her to tidy it.
I brought a bin for her room and I then replace the bin bag when it’s full.
I told her that I’m not cleaning her room but she can ask for my help and although it’s not perfect she does ask me to help her now when she gets overwhelmed and then for the next few days it stays a bit tidier.
Its not perfect but it’s getting better.
I assume there’s no way your DDs can have their own rooms?
I feel really sorry for the 18yo in this but I would provide a bin which I would empty regularly and then leave it up to DD.
Tell her to put the rubbish in the bin and if she doesn’t then it’s on her.
You need to pick your battles and if she wants to live in a pig sty then so be it.
Tell her if she makes an effort to put rubbish in the bin, then she can ask for your help if it gets too much.
Just the process of asking for help and you doing it will help towards strengthening your relationship.
Obviously there are much bigger issues here and these need to be dealt with more than the rubbish in the room.