i personally hate horses, i'll ride them when i have too and riding them is fun its just taking care of them that isn't worth it. all the work done with a horse can be done with an ATV and they don't poo everywhere. But as for health risks, i don't think there are any. i never took lessons but can and do ride horses when the oportunity arises (someone needs help with something and they only have horses instead of atvs) i don't own any but i would encourage you to go ahead and get her the lessons, a child not being afraid of an animal that big is a good thing and you learn how to behave around large animals so you don't get hurt, just a note, don't wear a mask, even with the dust, it'll spook the horse and someone will get hurt