Good question.
If you think she'll retain information from lesson to lesson, go for it. Ensure that you spend some time finding an excellent resource or teacher for her to start learning from because you want to start her with the best and most basic information possible. If she starts developing bad habits at an early age, they're only going to be harder to break down the road. If she starts developing great habits at an early age, she'll be amazing down the road.
I teach percussion students as young as 6th grade and can tell you that quality repetitions of basic motions are some of the most important things you can do for a young student. The more conceptually challenging concepts will have to wait until she's older and has the brain power to process it all - that's just life - but getting her quality instruction that will guide her through quality repetitions of fundamental technique habits will really go a long way.
Hope this helps!
