Hi W. - If she is already going through puberty and wearing deodorant, let her shave every few days. It sounds like she really needs to. I am speaking as a 5th grade grade teacher AND a woman who went through puberty at age 10 myself! It can wreak havoc on her self-esteem if she is self-conscious about being "different" or more advanced than the other girls, and can't so anything to make it a little better, like shaving to remove some of the hair. Just teach her how to do it gently and let her shave just a couple of times a week, or whenever she has time. Don't make a big deal out of it, just let her be educated and come to terms with what works for her.
I have dark hair and I'm half Armenian, so I was blessed with the hairy gene, and as a young girl it was really hard for me to feel okay with going through puberty early. My mother always helped me try to use strategies that would help, like shaving or making sure I had clothes that fit my body, not just what was in style at the time. Once all the other girls caught up, it got much better, and today I'm very athletic and happy with the way I look. Anyway, I see the social dynamics that go on with 10-year olds and I think it's important for your daughter to feel good about herself but also do what's best for HER, even if 10 seems young to you. I agree, it is young, but know that so many girls go through puberty at that age. You should see the range of shapes and sizes in my class any given year, boys and girls alike! Good luck and don't worry - it will work out okay for both of you!!