My kiddo has been taking lessons on and off since the age of 5. They haven't been consistent until the past 6mo because of weather, trainer moving facilities and other extenuating circumstances. Attention span is the hardest part, her lessons right now are limited to 30, maybe 45mins. As soon as she stops paying attention, my trainer ends the lesson.
She walks, trots, canters, goes over small jumps and as my trainer usually has me ride one of her beyond calm horses during the lesson, she's learned about leg yields, half-halts and other things I have been working on. Right now her focus is on her 2-point position since she's convinced she thought she wants to jump (not so sure about that, her pony over-jumped last lesson and now she's thinking that staying on the ground is good! LOL).
Find a qualified instructor with LOTS and LOTS of patience, take it easy and she'll have fun!