The teacher was way out of line, I have already said that.
But, alot of ballet schools and music teachers etc etc get parents who send their kids for lessons never intending to pay. I am not suggesting that the OP's friend is one of these parents but that line in her letter does seem to suggest that she thinks if she was in financial difficulty then she shouldnt be hounded for fee's?
Absolutely NO WAY should the teacher have said this to the child at all, under no circumstances was this okay. So on that YADNBU