@blossom2231 - there is a book called Divas and Doorslammers, about how adolescence affects children. According to the author, Charlie Taylor, a child’s brain is actually retiring during adolescence - structural changes are happening. Whilst this is happening, they can, and often do, lose certain abilities - like the ability to see their own needs in balance with other people’s needs - which can make them seem selfish. They can’t see that they aren’t the centre of the universe, they can’t control their temper or their impulses, they lose a sense of proportion.
He describes this as a form of temporary brain damage - but the important word there is temporary, because he says that, once the retiring in their brains settles down, most or all of these abilities come back.
I am saying all this because even though it won’t change the way she acts, it may help you cope better if you understand that it isn’t all deliberate bad behaviour - a lot of it may be down to changes happening in her brain.
It will be useful information if your dc becomes a sullen, stroppy teen too. They may not - two of my dses got through the teenage years without too much drama - but then ds3 hit adolescence, and it all went to hell in a handcart. Much door slamming, yelling, anger and name calling - my mum said it was my just desserts because the other two had been relatively easy - but he did come out the other side, and is now a kind, well adjusted, thoughtful young man who we are very proud of.
Apologies for the essay - I hope it helps.
One thought - when your baby needs a bit more space, could the bigger bedroom become a mixed use room - a bedroom for your dsd, when she is there, but a playroom the rest of the time? Might your dh accept that as a compromise?