I am fairly certain he's talking about her head from her ingame sprite going up and down one pixel every few frames. I can't find the video again, but it was impossible to unsee.
https://www.youtube.com/watch?v=sDaSw4E9-xM#t=29m38sTo be honest, I am not seeing it.Edit:Ok so it isn't her idle pose but during her ball throw into laser attack thingi spell card, her attack pose / sprite her head seems to go up and down indeed. So am I missing a meme or something from Japan or?