One of the greatest achievements of Bookworm as a series is the way in which the plot advances as a consequence of the cumulative actions of the characters instead of being some fiat dictate of the author. If you examine each plot development, you can see how what the things various characters did, even minute ones, led up to that development. Case in point with Corinna, another thing she did was consent to Benno helping Myne when she entered the temple, because at the end of the day, the Gilberta Company is her store, not Benno's. She could have said that Myne wasn't worth the risk, but she believed enough in her brother, and cared enough for him and the memory of her own good friend Liz, to risk her store for Myne's sake.