A question: Madame Morrible (SPOILERS SPOILERS SPOILERS)

Madame Morrible showed herself to be a pretty powerful witch. She rearranged clouds and was subtle enough in doing it that no one noticed. She jazzed up a tornado powerful enough to reach into another world and pick up a house, and was so accurate with it that she was able to drop the dang thing right on Nessa.

So why did the mighty Madame just fold when Glinda confronted her?