Hi, I am new to the forum but I have enjoyed reading here for long time.
I finally made an account because I feel like maybe what I could say on this subject is worth something to someone.
xlionesss, you asked the question if this girl and her horse look safe. No it does not look safe. But safe is relative term.
I teach riders and work with horses for a living and 9/10ths of the people I teach come to me out of fear of their horses. Fear of falling off, fear of being kicked, fear of being killed, etc. The darndest thing is, most of these people have relatively friendly easy to work with horses and all the rider wants to do is overcome their fears.
I have personally had horses who Spanish walk, rear, lay down, bow etc. I have even worked with beginning steps of Haute Ecole maneuvers. I have had accidents doing all of them, thankfully non of my accidents were fatal. However, I still work with horses, and I still have them do these things.
Something that I wish more equestrians would come to grips with is that fact that nothing about horses is safe. Horses are not toys. They do not come with direction manuals for safe operation.
The question is not if this girl is safe, the question is what risks each of us are willing to take. If you are not comfortable with your horse rearing then DO NOT DO IT, but be kind and reserve your judgment against others. This girl has made her own choice to work with her horses NATURAL ability and desire to rear to create a deeper and better relationship. She did nothing worse or more dangerous then the Spanish riding school does, or movie horses do, or trick horses do. She did nothing worse then you do with your horse. You simply think you are safer and better because your horse doesn't express his/her natural ability to rear around you.
For thousands of years people have ridden horses, worked with horses and yes, have had their horses rear, strike, sometimes even kick. Who are we to decide who should have done what for what reasons?
If you are not comfortable, confident, and competent around a horse then your chances of getting injured jump dramatically, no matter what your horse does or does not do and no matter who did what with your horse.
Lastly, Please understand, I believe everyone should act RESPONSIBLE around horses. To me responsible is understanding that horses are 1000lb, living, breathing beings who naturally have pride and hierarchy, who naturally rear, kick, gallop, bite, strike, buck and stretch. I guarantee this horse reared in his field by himself, before she ever had him rear on purpose. She did not TRAIN him to rear she just developed it into a form of deeper communication. Horses don't need your permission to act like a horse and will do what they will without asking you, when the need arises or when they feel like they should. Horses ALWAYS have a reason for what they are doing. Only humans do things "just because". Whether you understand or are aware of why your horse does something is entirely dependent on you. Responsible is, respecting horses for what they are and can do, not behaving like a fool, being aware of what is going on, and understanding how horses think and behave. No one is ever safe, or ever will be, but it is possible to limit your risk of injury through understanding knowledge and awareness. If you do not have the understanding, knowledge, ability and awareness to communicate with a rearing horse in a respectful manner (both your horse respecting you and you respecting your horse), then DO NOT encourage rearing in your horse or you WILL get hurt. In like manner, respect others and understand that different people can communicate with horses in different ways and are willing to risk more, and those people do not need to be put down or insulted.
"Kindness never hurts but cruel words can poison the soul."