I'm thinking some sort of hot meal, that then blocks her vision

Or perhaps some kind of stew that that nullifies ocular senses for 1/7 of a week?

Seriously though, whose stupid idea is this? Is this a thing that moms everywhere say to there hair-biting daughters? "You need to stop with that nasty habit sweety, our some day soon you'll find yourself unable to see after lunch, and I'm not gonna tell you for how long!" And in the schools, stories go around like "Sally Newman was blind for a whole day last week, and she says her mom served her a stew that made her blind to make her stop biting hair!"???