My daughter is now 11, SWCAH, and right about age 7-8 she noticed how much hair she had and it really started to bother her.  Her legs were extremely hairy, the hair was about 1.5 inches long.  Her pediatrician said that it was up to me if I wanted to shave it.  So we did, I had to do it twice and then throw  the razor away.

She’s been doing it herself since she was 9.  We use the Schick Intuition.  I don’t even think she’s ever nicked herself.  Just in the past year we have started using Nair for the face.  She does her upper lip every couple of weeks.  She has a lot of hair on her arms but it doesn’t bother her, yet.

It’s really when you feel your daughter is ready to tackle the shaving, waxing, plucking.  Our doctor and endo didn’t see any problem with her starting at 8.

Good luck