I knew a girl when I was a kid that was basically fully developed (and really hot) by the time she was 12. I really felt sorry for her back then because she was simply not equipped to cope with an adult body. I feel even more sorry for her now.
Traci Lords used being early developed to her advantage and got away with it.
My twin girls were like that. It was hard on them.
One of them also got seizures at 10 because of puberty.