Just because she didn't injure the horse doesn't mean its not abuse. He started to flinch when I would go to pet him after that. So just because it doesn't leave physical scars doesn't mean there won't be emotional scars.
Very true.. it was a very over corrected angry response. If a horse flinches that doesn't usually flunch, he's worried that he's doing something wrong.. he doesn't know WHAT, but he's worried about being hurt. At least that is what I have seen in my experience. Instead of abuse, I'd call it bullying.. and it needs to stop. It's not productive at all.. I'm glad you're moving out of that barn.
A horse can also flinch if he's not sure if it's a good thing he did or a bad thing. Being flight animals, they typically choose to flinch rather than stand and wait for the response from the trainer.
At the same time, if he was in her space and not being respectful, then she probably just used what she had to get him to move over NOW. If it's a one time thing, then it's fine. If it happens over and over again.. she's being an ineffective trainer which does nothing for the horse OR the students. I've used the hoofpick in my horse's tummy for slamming his foot down on the farrier. He doesn't do that anymore, but neither have I.
I've seen a few ladies kick their horses in the belly.. I would never do that. I rather send the horse away and "work" or back up or leg yield in a circle. But just because I don't do it, doesn't mean it's abuse.. it is a very immature response if the horse didn't do anything dangerous. If he did something terrible like charge at you or rear, then it could be well deserved. Horses out in pasture do worse.
I wouldn't jump to conclusions though.. and watch that you don't praise a horse that is being rude. It's very easy to feel sorry over nothing and then you end up praising the horse for being bad, which makes them act out worse.. etc.