If you ask me this is no different from (what's that show?) Cavalia. The only difference is she's posting for free online and her material doesn't come stamped with the "do not try at home" sticker. Really I don't see any
difference between the two. (Maybe that expensive horse show doesn't have rearing. I don't know.)
Person on the ground controlling the horse? Check.
Horse performing enviable tricks? Check.
Helmet free work? Check.
People swooning over "amazing bond?" Check.
Good horse people doing what they love? Check.
Really I don't have anything to criticize her on. She's infinitely more in tune with that horse than I could ever hope to be with any horse handed to me. She's an infinitely better rider than I could ever hope to be. The horse clearly respects her boundaries and he seems like he's always questioning "is this ok?" when I watch his head. He's eager to please.
There's always going to be stupid and impressionable people on the internet. If you ever want to lose faith in that, simply google "fail videos" and be amazed. While this woman shouldn't be trying to say what she does is easy in any fashion, and while she should be promoting caution, I don't think I (personally) have room to speak or reprimand her for the way she's doing things. The only thing I could do within reason is suggest a helmet.
ETA - I found a clip of Cavalia. While it's not exactly the same as the video in question, it shares the same principles. Especially where she's running in front of the horses.