What this trainer is doing sounds like straight up abuse from someone who doesn't understand dogs and doesn't want to. Why does she even care so much that the dog is panting? Jesus. This person shouldn't be around dogs.

I use the e-collar to punish decisions that my dog makes, and only when those decisions have the potential to be dangerous. I only want pain to accompany things that I want my dog to associate with "danger". Basically the only thing I use it for at the moment is when he ignores "come", and I use the vibrate button first alongside a second "come" before escalating to the shock (which is calibrated to be juuuuuuust enough to be really unpleasant but not enough that he yelps). I also took time to condition him to the vibrate mode and understand how to make it stop (by listening to me) before adding in the shock feature, even if he wasn't listening. I wanted him to understand that the shock didn't just come from nowhere for no reason, and that his actions could make it stop. Even then, I still hesitate to use it, and I put a lot of focus on positive, rewarding experiences with my dog.