Hello, I really like your story. I think you have a great story going, however I have a few 'concerns'.
1.) when Maddie pulled her horse up in the middle of a lesson, that was confusing, and a tad unbelievable. Either she's got a great relationship with her trainer or, her instructor's a push over... If I ever pulled up in a lesson and just felt like I'd jumped enough, my instructor would not let me just leave. She would never stand for that attitude. Now then, if that's the relationship you want them to have, that's perfectly fine and maybe that's how it is in the Olympics. (Though I doubt George Morris would take that kind of attitude either...)
2.) I highly
dislike the part where Lauren tells her students to 'look for shadows that may spook their horses'. Most Olympic caliber horses wouldn't be all that spooky for starters, most Olympians would be paying attention the the next jump, watching the time, looking out for uneven/dangerous footing etc instead of worried about if their horses is going to misbehave. Perhaps they could say 'look to the next jump' or something like that?
3.) I agree that their should be more character development. The characters need to have more 'personality' . They shouldn't all be perfect either, even Maddie should make mistakes, people tend to get annoyed with overly perfect main characters. You should create more drama.
4.) I'm a little surprised that Lady was unconscious or unable to move with just those minor injuries. Lady is an extremely fit event horse and she lays perfectly still with just some cuts and tendon issues? The barn where I work at has a horse that broke his pelvis, in his paddock, he was still limping around when they found him. IMO those injuries aren't going to cause a horse to just lay quietly, most horses would thrash around, scream, try to run away/limp around etc.
4.) These people ride a lot
. So they go for a trail ride, go galloping over cross-country fences, and then do a group lesson that involves show jumping, dressage and cross-country! That sounds like a lot for even the fittest of horses and riders. My instructor does prelim at the moment, she did intermediate in the past. She hardly rides her horse longer then 30 min, same for the horses she is training. During show session she would take an hour weekly lesson, but that's it. No one at my barn is in the Olympics, but that still seems like a lot of riding time. Even if you want them to be energetic, I think you still need to tone it down a little.
5.) I think the publishers found this too 'horsey' not because of the technical terms, but because this kid has no life. People don't want to read the truth, how horsey people practically live at the barn.
They want to read lies, they want drama. You should talk more about school, Maddie's 'non horsey' friends, her home life things like that. As other have said you should include 'teenager-y' things, getting a licences, getting a job, meeting people, school dances (even though I hate romantic books
some people find that interesting.
I am not an expert on eventing. I am just beginning to discover the wondrous world of eventing. I work at a big eventing barn 4 days a week and hope to compete in this coming show season. I am no an expert on writing or eventing, this is just my honest opinion, so take it with a grain of salt.
I wish you the best of luck, and look forward to seeing how this story develops.