Wow ... I am not in your shoes but I wish you could have stood up during the meeting and said in a calm tone that abusive comments such as hers will not be tolerated and walked out to go find the principal immediately. But I am sure you were shell shocked to say the least.
Given she is the only GATE certified teacher and on top of that she is not responding to your emails and note means you really need to voice your concern to people above her. There are channels and definitely go up the chain. Plain and simple: No teacher has the right to treat a child in that manner and if she did that with the parents in the room I could only imagine what she does in the classroom when it is just her and the kids.