What happened to Meg because of Mrs. Which's mistake?

They all then begin to disintegrate again, and Meg holds Calvin’s hand. A mistake is made, however, and Meg finds herself feeling crushed and flat. She can’t expand her lungs and her mind won’t work correctly either. She hears the words “Oh, no! We can’t stop here! This is a two-dimensional planet...” and suddenly Meg is thrown through time and space once again where she regains her sense of life.