What age are we letting our little girls shave?

My step daughter has started shaving her legs. My husband did not agree with this and thinks she is far too young, but her mom is encouraging it and allowed it. I do agree that she seems a bit young for it. She is not an extremely hairy child anyways. I have been around since she was 2 years old. My husband and her mom were young when they had her and it has always seemed like my step daughter and her mom have a friendship dynamic more than a mother-daughter dynamic. I am not bashing anyone here, I respect her mother and even like her. I just don't want my step daughter to feel like she has to grow up so fast. She acts like a teenager at 8 years old. Just curious what other peoples thoughts are?