Although Chi-Yun might be the most powerful member, she can't do everything. She was so keen on having the strength of an elephant and the body of a centrefold that the hide of a hippo got lost by the wayside. She's young and naive and so she doen't always use her power in the most sensible way.
Besides, it's easier to write a fight scene when less people are involved, and keeping Chi-Yun out of the way made things a lot neater 
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To want in one's heart to do a thing, for its own sake; to enjoy doing it; to concentrate all one's energies upon it - that is not only the surest guarantee of success. It is also being true to oneself. -- Amelia Earhart
