Not quite but almost. Was on a very turbulent cross country and the lady behind me could not stop vomiting - the coughing, gagging, wretching kind that has you moaning. Poor thing had a completely empty stomach but still couldn't stop.

I have a very weak stomach and almost lost it because of the sound effects behind me. (I was a middle seat and so was she) She was leaning forward most of the flight so even closer to me.

As for etiquette - I think her seat mates knew her - if not - they had iron stomachs. The just sat there and stared stoically ahead. The FA came around and offered her a few extra bags which I think she just left on the floor upon landing.

As for her condition - I think she was on something because in the waiting room she appeared to have the very glazed look and when we had seen her earlier, she seemed very enthralled by the light show in Atlanta Harstfield airport.