Just wanted to ditto what has been said here. I don't think any study would find any corrilation between what age a girl shaved her legs and when she had sex.
My daughters shaved their legs, pierced their ears, even cartlidge piercings in middle school, had purple & blue streaks in their hair durring the summer. We are very religiously conservative, and my girls always and still do dress modestly. You have to give them some harmless outlets that help them to fit in or feel a little radical. If you supress them too much then they do rebell and may want to fit in by having sex at an early age.
Surprizingly, when some of the old ladies at church ask, isn't that your daughter with the purple hair & I said yes, their response was, go girl. They knew my girls were nice and that a little purple dye is harmless.
I don't know if my mother would have approved or not, she passed away before my girls got to this age, but you have to do what YOU think is best. Only you know what your daughter needs.