My parents put me on a leadline pony ride at a country fair at the age of 5.
From then on, I was desperate for a horse, and finally got one at 14.
One of the things I’ve always loved about horses was the autonomy and independence, plus having the interaction with an animal on and off the ground.
There weren’t a lot of intelligent adults around, but by the time I was 14, I was able to figure things out and teach myself how to ride with help from other kids.
When I look at kids today getting into riding, it all seems so much more oversupervised and limited, like taking skating lessons at an indoor rink once a week compared to having a pond out behind the house.
I would say, at her age, maybe start by finding a pony situation where you can lead line, let her groom and handle pony, and get comfortable around a pony before you start going for actual lessons. Make the pony time fun. If the pony is in a private or semi-private situation where you can lead it in a field, and let her interact with it safely without being surrounded by impatient dressage queens in an adult training barn, so much the better!
then when she has some balance and can walk/trot in hand and seems to enjoy being with horses, you can find a good riding lesson program for her age group.
Ideally, not lesson horse that are balky and cranky and that will teach her bad habits of kicking a pulling.