Madame diLustro is described as a fine cook and an excellent detective. She often hosts dinner parties and flies into a rage if one of her guests arrives even five minutes late. Snicket has to dash off to one of her dinner parties while in the middle of writing The Reptile Room.
Later, when Lemony Snicket describes good opening sentences for a dinner, he includes "Madame diLustro, I believe I've discovered your true identity!", described as a phrase that would be able to lead discussions, arguments and accusations, making dinner a lot more fun. This implies that Madame diLustro is not her true name or is a disguise.