Wow, I am so sad this happened, and that you felt you had to leave. I completely understand, though. In your place I would love to be strong and assertive and all that, in real life I would probably be furious and mortified at the same time and never say a word. I did think of one thing that might help, though - write a note to this woman. Explain what you heard, what it felt like, and how you've now left because of it. IME people are often thoughtless and stupid, not truly vicious. It might make you feel better, and it would certainly make her think. Ask the teacher to hand her the note if you don't want to ever see her again. Just a thought.