Is There an Appropriate Time to Brush Your Teeth at an Opera?

She was using a full sized toothbrush with no tooth based that I could see and she was brushing very actively. What would have been the appropriate response to this heinous opera crime? It's not a time thing it's a place thing because you can't brush your teeth at the opera or outside of your house bathroom only. She threw her toothbrush loose into her purse turned to me and said I really thought I was late to this but I guess I was just on time. That was speechless and I just stared at her.