Me and my mom just started training my horse Andie. she is 4 years old and we're trying to break her in a little more(she's a green broke and still has a lot of training to do). I've noticed that every time we lead her into the barn on the lead rope she rears in the door way where the barn leads out to the pasture.
She's done this since we've had her (about 4 months now). I know it's incredibly dangerous when she does this but I'm not sure how to train her not to do that. usually she does it once and with a little persuasion will start walking again. We do have and older,more experianced horse with her but she still does it.
Is it like a black stallion rear? Or just a hop? The two are very different, and it kind of depends on the situation. If the mare is pushy on the ground or shows lack of respect, there is your problem. If the mare seems frightened, then maybe she had a bad experience in the door of a particular barn. Like I said, depending on the situation, it needs to be dealt with differently.
If the horse seems scared or anxious, repetition and correction is going to most likely work best. I would not let her go until she goes through the door without rearing, or at least improves. Then when she is calm, let her go to the pasture. Do this daily and you may see improvement. Like I said, if she's scared you need to find a balance between getting her to respect you and realize that rearing is not acceptable, while at the same time reassuring her that it is going to be okay.
if the horse does not seem scared or anxious, then man I would be on that horse like stink on poo. I would make her think she is gonna DIE for rearing. My mare did this when she was 2 years old and quickly learned that when she reared, she got hit with a whip HARD in the chest. Thus rearing became a no-no to her.
See what I mean about the context? Depending on the situation, you will get different results. Depending on the background and what the horses demeanor is when she rears really will tell you why she is rearing and thus you can fix it.