R.D.
I use Thai Deoderant Stick...it is made from natural ingredients that don't let the bacteria (the cause of BO) grow. It does not contain the harmful aluminum and carcinogens in 'regular' antiperspirants and deoderants. It is more expensive initally (around $7?), but they last a LONG time! I am still using the one I bought in June 2006!! It will be replaced soon, but still....think of the money I saved in two years of not buying deoderant every month or so!
I would try using this first, especially since she is so young. It is a much "greener" and healthier choice. Make sure she uses it correctly (wet it before applying to clean armpit). Good luck and let us know what you decide to do.