Please don’t worry about the other stuff (not being an only child etc).
The teenage years are when the brain undergoes huge changes. Different parts develop at different rates. The part that likes excitement, novelty and risk develops before the rational, empathetic part catches up.
She is just developing as evolution intended. She is hardwired to seek a life outside of the family. It does feel like a personality change. If she was a loving child before, she will be a loving adult again.
It’s all about making sure they stay safe at this stage (alcohol, drugs, sex). I would tell my Dd that I wasn’t trying to stop her having fun, but she needed to be aware of these things. All you can hope is some of this stuff gets through.
You werehappy with your parenting til she was 15, believe in yourself this will be enough to get her through the next few years.
How to manage in the here and now? That’s up to you and what you are happy with and what the personalities are.
I personally, ended up having a blow up with mine. Because it was so unusual for me she did take notice. You need to find that fine line where she takes notice of you without it descending into outright hostility.
Like a toddler, good behaviour gets rewarded (lifts, money), and bad behaviour gets nothing.
But do look up the brain thing. I believe Prof? Susan Black is the leading expert on this.