This is so hard! She's still your baby!
At her age, my mom wouldn't let me shave my legs either, and I was supposed to wait until I was 15, too :O) After becoming a parent, it really does sound like the a good age for it, BUT..... it's not. Girls bodies are developing at this age, and that includes getting hairy legs.
I would teach her how to shave them properly :o) You want her to keep coming to you first, so after further-thought, let her :O)
At her age, I went behind my mom's back and shaved my legs. My mom was moritifed! So was I! I had never done anything without my mom knowing before. The weather is turning and it's almost time for shorts, so it's on her mind more than ever.
Now the eyebrows..................for whatever reason, I feel TOTALLY against the eyebrow plucking. I also have brows that need constant "attention" since her age, but it's just a whole different responsibility, and it's on her face, so it will need constant attention!
I think 15 is a good age for plucking :O) That's when make up starts, and it all goes together.
You will be a wonderful mom if you say "yes" to shaving her legs :O)