I've been weighed at the end of sessions before, with no complaints, a few people regularly come in mid-session and nothing negative is ever said.
I don't think I would to go back to the class if I was told off like a 6yr old, in fact it happened at an art class I was going to, I was taken aside at the end of the lesson (about a class I'd previously not completed) and had a good old telling off, and I never returned. I hate to be made to feel like a child.
I would complain and explain how she made you feel, even if your confidence isn't at rock bottom, the next person she speaks to like that might be. xxxx