Well she is a world renown trainer and has worked thousands of horses so I tend to think that it would be better for you to pay a little more attention to her and not dismiss her out of hand.
Granted that, but does that mean a person has to yank on the horse's mouth to respond? The horse was trail sour, so put her feet to work; don't yank her around...she's already in a reactive state. Yet, This is exactly what she was telling the owner to do; not simply take up one rein and bring her nose around, no it was literally, you need to pull her hard to a stop, yank her into a back up, and then pull her head around.
I know that there are different methods of training, but I will not ask someone to yank on any horse to get them to respond...sure she got the horse to do what she wanted, but that mare was extremely tense; exactly opposite of what I look for in a horse who is understanding what I am teaching him...I want a relaxed feel, and appearance; when the owner got back on, the horse relaxed, was paying attention, and the owner was giving subtle cues, not simply yanking on her mouth.
I will be firm with a horse, but I will not "pop" him in the mouth with any bit, especially a gag type bit...that style is already 'loaded' with alot of power. Teach the horse to give to soft feel.
She did have good ideas, in that the owner needed to learn how to control the horse's body, and determine the path...yes, this is great, but that's where I stopped agreeing with her, once she started applying her 'method' to getting the horse to obey her. The horse listened to her because she was yanking on her mouth, not because she was challenging her mind.