He does do it again, but only because there are more monsters. His Blizzaga brings down a smaller pair, and then there's enough of a lull that he turns to her, irritated.

"I am not your mentor. If you cannot do magic, then I cannot teach you."

He's probably going to regret phrasing that as an if instead of a flat-out 'no,' but then she hasn't really been processing 'no' anyway.