A point has been made that I think is worth acknowledging. It’s not a terrible thing if a young person loses interest in riding. Kids go through enthusiasms, a sport or activity is the whole world to them for a few months, one or two years, even a few years. Then they pass through a maturity gate and suddenly that thing is no longer The Thing.
But they take something away that is worthwhile and helps them throughout life. And sometimes they will come back to horses (or another sport) later in life, often after they have their own career, income, even family. Maybe put their kids into riding lessons.
Just like tumbling lessons, music lessons, and other things kids do but don’t stick with, riding lessons can become important life experiences. A kid picks up some confidence and loses some fear.
If the parents are more into it than the kid, that is nothing new when it comes to sports. I have a feeling the insistent little girl who wants her own horse is likely to also be the one to say “the green horse isn’t working out like I thought” and pull the plug.
All an instructor/trainer can do is watch from the sidelines, sometimes. And choose the healthy distance they need to have for themselves. 