So I lease a QH and we have come really far. I have spent almost a year using natural horsemanship and doing lots of ground work and playing with her. She backs up well and is respectful of my space... except when she sees one of her pasture mates (specifically two certain ones). When the owner of one of her pasture mates bring the horse in, my horse will start using the reactive side of her brain and pace, lift her head high, blow out of her nose, flare her nostrils, and act as if I am not even there getting into my personal space. I have tried back her up and yielding her hind quarters to get her attention back to me, but she still does it.