Every person is an individual. Whether that's a person old enough to have their own children, or a child themselves. That means that every relationship between two people is unique. What communication technique works for one of my girls doesn't work for the other. My wife's relationship with each girl is different to mine. If you put the two kids together it's like putting cats in a bag.
(Of course all previous rules and preconceived ideas go out of the window when the wind changes direction. They are teens after all).
In our house it's not so much the issue of shaving leg hairs by the older daughter, it's the furry tide mark that she leaves in the bath. The younger one at 12 hasn't bothered with hair being a "problem" she much prefers to wind up her sister.
Hairy leg problems are an opportunity for you as a parent KK to hone your relationship, especially the listening part. I don't know whether you're good at it or not, I've not asked your children. I'm saying this because the hairy leg thing really doesn't matter. With my elder daughter we have gone through much more in the way of challenge:
-age 13/14 and all the peer group girls trying sex for the first time.
-experimenting with wrist marking/cutting
-not eating properly for days
The funny thing is that she is a happy, healthy, mentally stable, fit, tall, pretty creature. She tinks that she's inwardly insecure, but that's just teen times.