In the 'girl turns into food story', it could be that she enters a world where the laws of nature are different. There could be a mad scientist or a powerful entity that changes her into food as part of an experiment or a power play. It might also be a metaphorical story, with the transformation representing something deeper like the loss of identity or the objectification of a person.
Well, it could be a fantasy story where a girl magically transforms into food. Maybe it's due to a spell or some strange magic in a fictional world.