Shizuku was a swordsman who specialized in speed, so her defense was extremely brittle. Evasion and parry were the basic of her defense. Besides, damages would accumulated little by little from “Magic Shock Wave”‘s after effect. Also, she could neither completely evade nor parry.
Following that, Shizuku’s movement had slightly become duller because of the accumulated damages. And that was fatal in a fight to death such as this.