When you do shave yourself, I wouldn’t do it in front of your children. They may think they need to do it too to look pretty

I would say never Why would you ?
Encouraging her to do so, means telling her that hairs on the legs is not pretty or
encouraging her to do so, means telling her she’s more beautiful without the hairs on her legs,
which is not a healthy message for a 12 year old.
Tell her she’s ok and beautiful as she is.
Teach her inner beauty is far more important then outward appearance.

well this is up to you and your daughter. when she is ready or has the want to shave her legs is probably the time. There is no rush or time limit. I shaved around that age. just going into to highschool was my motivation of trying to act like a grown-up lol.