Chewing the bit is a good thing, shows they are relaxed in the jaw and accepting the bit. You shouldn't want to stop it. unless you mean in a frantic way in which case she may be finding the work you are doing to stressful, don't strap her mouth shut as that will just upset her more as I think...
Of course you can put a horse behind the vertical on long reins, every time he goes to stretch his nose forwards she clicks at him to get his attention I assume, them gives a little pull of the reins so he brings his nose in, you do talk sense though, and your comments about this horse are...
I watched the first couple of the schooling sessions, and then could not watch anymore as it was depressing me, I thought I would take a look at this one thinking there must be an improvement, I was wrong. How can you allow this rider to do this to your horse? It is disgusting. She insists...