This has been bugging me for a while. I understand why Zuko took that lightning for Katara. But why did Azula shoot it at her? She was very calculating and had no way to know that Zuko could redirect it. She could have ended him then and there but she changed her mind last second. So why did she shoot it at katara as she called a filthy peasant? What would she have gained from it if it did hit her?