There's a whole lotta stupid out there; this is a good example of it. Horse's mind was already off of 'bucked that annoying thing off' and wandering elsewhere when she started hitting him. To him, he was being punished for standing there.
See this was all that I was thinking....he looks like a very good horse and with her spurring and pulling your asking for a buck....I've ridden bigger bucks than that and stuck to the saddle like glue. I also HATE that she's smiling when grabbing the bit and you guys are right timeing is waaay off. I feel bad for the boy I do. Having the horse fear you is only going to lead to more complications down the road. ~sigh~
Edit- Also notice it's the camera person handing her the whip ~double sigh~