“Namaste” is inappropriate?

Went for a yoga class and there was an Indian girl there. She seemed to be an experience practitioner. At the end of the class, the yoga instructor asked everyone to join their hands and say Namaste to everyone in the class. When the India girl was leaving the class without doing so, the instructor asked her to say Namaste before leaving. She responded saying that she didn’t think it was appropriate.

Just wondering, what other thoughts are on this?

EDIT: just to clarify, this was my first class with the instructor. I too thought she was a little aggressive!