Not sure why you started two threads about this..You're going to get the same reaction. It isn't cool, she's not being naughty..That is a very dangerous situation that can hurt your horse and you. You have no idea whether or not she's going to flip over, all it takes is that one fraction of a second and you could be dead. There are other ways to handle it besides letting her do repeatedly for three hours. She could even have hurt herself just having to do it for three hours, it's an unneeded stress on her body, not adding the fact that you both could end up severely hurt. I hope you rethink your strategy and go about fixing this behavior in a safe way..It is possible.
I'm sorry, I get heated about these things, I had to "fix" a horse that had a rearing problem and it took time and constant working to correct the behavior then most people think it's cool or amusing when their horse does it..I'm not one of the people who want to tell you that you're a "good rider" for staying on while she was doing this, a good rider would have gotten off and not kept risking your LIFE by staying on.
Do not take this horse's behaviour lightly, it could get you killed in a second. When I was a youth, a girl in our group of riders had a horse like yours, didn't want to leave the pasture to go for a ride. This was also a horse that had been at a trainer's to solve the rearing problem. Well it didn't work, the horse went up & over (first time we know of, but the last for the girl), she was killed. I took only one look, I saw blood coming out of her ears. From that day forward, I will never, ever get on a known rearer. Remember, all it takes is a second & when you're dead, you're dead forever.
Not everyone is aware of the other thread. YOu can post a link to it in your next post. But , you cannot blame them for giving advice that you have already received. If it's redundant, just ignore it, ok?