There was a thread on here that I saw which explained that teaching them the "circus bow" is not a comfortable, safe thing to teach them. (It is better to do the bow on one knee, as shown in my picture above) It is possible it was hurting her and you continuing to ask her she just had enough. Did she show any signs of discomfort leading towards her freakout? Ears back, tail swish, or just resistance in doing the bow at all?
Did you correct her when she started getting aggressive towards you, I hope?
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