I've been reading about this sort of thing b/c of questions I have about my own children. I'll try to be cohesive.
. And it could tie in the climate connection.
I got my menarche when I was 9. My mother got hers at around 10-11. that sort of fit, in the whole girls are like their moms POV.
I also, as a child, had a big problem falling asleep at the socialy expected time. I was put to bed at 7:30 (at say 9 years old) and lay there awake until 11:30.
My eldest child is exactly like me. Even as a baby, he had trouble falling asleep when he *should* have, but passed out easily 2 hours later. While we were receptive to his needs to not be forced to stay in bed, we also felt, as parents, that he *needed* more sleep, it had me quite worried. I feel sleep is so important to health, recovery, growth, stress. by age 8 he was so upset at his struggles to sleep, and asked if he could take anything for it. We'd already tried herbs/vitamins years before, but he's one of the 4% who have the opposite effect of calming herbs; he gets wired. I've been taking melatonin as a sleep aid for a decade (though never during my pregs) and he asked about it. I researched it, talked to others/naturopaths, etc. And he started taking a small 1/4 tab. It worked fabulously. He was sleep in minutes whenever he took it, awake for hours without it. We never wanted him on it forever, but it gave him peace and we figured we'd just use it for now.
A year later he was still using it, and I wanted to research it more. I learned about delayed sleep onset disorder, which basicaly means some of us are wired to fall asleep 2-3 hours later than our social expectation. They do not know the cause, just that it exists and can be hereditary. That was me! I've always been a night owl as an adult, nd it fit my son as well.
So then I read more about melatonin, as the one thing I knew about it that worried me was that in rat studies who were given melatonin, it retarded puberty, delaying the process. And I worried that my son was approaching the 'early puberty window age of 10' and I didn't want the melatonin to be messing with his natural development. (he has since chosen to stop taking it and is right back to being the 11:30 pm night owl he always was. but he's okay with it now.)
I learned that melatonin levels drop in children sharply, at around age 10 (but it can be earlier) and his sudden drop in melatonin levels is what signals puberty to begin. Ergo, too much melatonin can delay puberty and mess with your cycles. Too little, and you have early puberty. This is why the Inuit, who live in times of permanent darkness in the North, have big fertility issues in their long dark winters.
It frustrates me that the media focusses so much on the sensationalisable aspect of hormones in our food (I agree, that's not healthy) and stears clear of the less-drama-or-scare-tactics melatonin connection.
So this fit even better with what I know of myself. I had trouble falling asleep consistently, for my entire life (lack of melatonin?) and I got my period earlier than most (drop in or lack of melatonin).
this could fit for your daughter as well. That it is not what you *didn't* do or did do in her parenting/health, it is simply who she is. I was vaginally birthed and bfed too, and had my experience as a kid. My son was vag birth, org food, no meat, bfed for 4 years, no-vax, co-slept, you name it and still has trouble sleeping early and may experience early puberty like me. His Dad experienced it very late, and has never had trouble sleeping in his life. And that reminds me again that while we often say 'daughters will follow their mothers' they also get that second X chromosome from their fathers, so who knows how it will all play out. Maybe my son will be like me and y daughters like their father.
I hope that helped, and wasn't clear as mud.