I found the suddenness with which my daughter changed to be the biggest shock. It was almost overnight - she was much younger than your daughter and went from wanting me to sit in the bathroom to chat to her for hours while she had a bubble bath to flinching and recoiling when I went anywhere near her.
It was so unexpected that it took me a long time to recover. My marriage wasn't going well at the time - I didn't know it but my XH was having a longstanding affair. Again, he and I had been very close and the distance was driving me crazy. It was like being ghosted by someone who was still talking to me, if that makes sense.
He left (with a footprint on his arse) and a year later my daughter turned against me. I've never felt so unlovable and it really damaged me.
However, she's an adult now and got better and better as time went on. I've always loved her as much as I did when she was that little girl who thought I was the bees' knees, and just had to have faith she'd come back to me. A divorce always muddies the waters, though, doesn't it? She couldn't blame him (in case he didn't see her again) so she turned all those bad feelings towards me. It was truly awful.
Do you think she'll go to university? If so I'd encourage her to go somewhere where she has to live in - she'll learn she can't treat people badly without consequences.
Just one thing - don't even think of giving her anything from the child maintenance. Absolutely no way. I would say it's not up for discussion. Don't cave in on that - it'll give her some power.
Similarly with child benefit. I knew mums who gave their children the child benefit - that's not what it's for.