The power of the master monk is not something to be trifled with, and Sheela's mix of martial arts and magic is sure to get her far this time around. And against a squishy little wizard boy, her might will do quite a number, indeed. While Vivi has a versatile bevy of offensive spells, he certainly lacks the speed and durability to handle more than a single assault from Sheela. More importantly, if he actually gets a spell off, Sheela can just make use of her handy healing techniques to get back in top shape. All in all, Vivi would be foolish to try and overpower the master monk - after all, her long-standing training certainly wasn't made to be trumped by little kids.