The folks who install the best ground manners, IME, are
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Natural horsemanship folks and by that, I mean the real-deal people who actually start colts and work on tough horses rather than those who market DVDs and crash-courses to people.
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Grooms at race tracks. Though those guys will accept slightly different things from their horses. We ammies want some of what they install and not others stuff. But they do get those fit babies pretty educated on the ground.
While books are OK, I think you might want to send your kid in the direction of YouTube videos. The first guy I’d suggest who fits the “not natural horsemanship” requirement is a European dressage trainer. Sorry, I can’t remember his name! I know he’s on YouTube. Or look up Warwick Schiller. He will look more like an NH guy, but I find his explanations clear.
The reason I suggest video is that the key to success here is the conversation between horse and handler. You have to see that in action. Even better, you need to have that conversation yourself with your horse, moderated by a good pro.
FWIW, I don’t think the solution to a kid who has a trainer, a badly-mannered horse on the ground (but you have a trainer?) and a kid who won’t listen to adults is *less adult" and more “learn on your own, but with the wrong medium.” The ability to train a horse cannot be learned from a book since the process is so dynamic and individualized! So I think that removing an adult that the kid has to listen to is a recipe for no training or unfair training for the horse. Again, I apologize for the unsolicited opinion, but this is a teachable moment where the kid needs more help from a good pro, not less. By that, I do mean that the kid should do the horse handling, with supervision and instruction. She needs to see the consequences of her decisions about the how to handle the horse. Presumably, her best thinking created a horse with poor ground manners. Let her see who a good pro can get from a horse with logic and good timing. Let her try to reproduce that, or do better without listening to that guy. It might be a bit of a PITA for the pro, but a good pro will appreciate that he/she is letting your daughter learn about the value of good horsemanship, too.
Best of luck to you all.