User blog comment:Goddess of Despair/Thoughts on the First Episode of RWBY and Stuff/@comment-4043943-20130724144825/@comment-7622429-20130725184757

That's the point. Since it's hard to animate people ACTUALLY putting stuff into their mouth,RWBY probably played on that fact by making her eat up the cookies super fast as though they just disappear to emphasize her "derpy/goofy/childish" demeanor,as well as the quirkiness and clever anime/cartoon tropes seen in many other similar series that don't rely on having the laws of science apply visually.