With two girls here I should be ready when they ask for deodorant, when my eldest ask for that, I was really panicking. Just then I realized with her age, she should starting using for it. As for the girls they start puberty between ages 8 to 13, so no wonder she asked for it since she is too active at school plus she has some extra curricular activities that need a lot of energy.
In one way or the other, there are some tips to in how to control body odor:
She should take daily bath and should be in the morning because there are less bacteria in the morning that makes their sweat smell.
And after they are done with their activity outside, they should take a bath, they could use washcloth and wash the armpits, genitals, feet to minimize the odor.
Their diet also have to be watch, check if they eat some spicy foods or garlic, as these can contributes too much for BO.
Wear clean underwear and socks everyday.