Sounds like she's trying to break all the personality out of your dog. Really at the pinning down wrestling move, I would have been out of there. I know when you were watching this you were probably too stunned to think it out, but now that you can reflect on it, go with your gut.
Totally agree with Gretchen, and I want to add a personal anecdote because from your post, OP, I suspect you are already beating yourself up.
I've been in your shoes, literally. A few times, I'm sorry to admit. But the thing is...you do your research, you place your trust in someone, you don't know that much about the subject, you pay good money...they do something you're uncomfortable with, but are you just being stupid? Maybe you're one of those dreaded "pet parents" that treats an animal like a human? Maybe this is how everyone does it, how it needs to be done? Maybe if you stop things, your dog is going to morph into an unruly monster? You don't know.
Except most people will recognize abuse, and it sounds like you have. It's just hard to label it as such, since most of us have a tendency to minimize stuff like that.
I'm a professional horse trainer and always had the goal of becoming one, and as a teenager I did several things I regret hugely because successful trainers told me to (nothing illegal or obviously abusive, but cruel nonetheless IMO, and I knew it was wrong at the time). I've also done the same with a dog once, on a smaller scale.
Now, 20+ years later, as a professional horse trainer and an experienced dog handler, I'm pretty immune to that kind of pressure. But most people aren't--the whole point of hiring a trainer is that you place your confidence in them, because you don't have the knowledge to train your dog on your own. It's really hard to stop things in the moment, especially because most trainers are also good salesmen and have forceful personalities.
No reason to let it continue, though. Don't feel bad for not stopping it in the moment, but do your best to prevent it from happening in the future!