Cao Cao Seems to Find Me a Bit Annoying

Looking for a Good Quick Transmigration Novel! The Female Lead Is Cute, and in One Arc She's a Clumsy Assassin

The heroine is a cannon-fodder character following the plot. She's the youngest in her organization, a ditzy assassin. In the story, a prince hires her to assassinate the hero. The hero is the emperor's uncle. In the original story, the heroine poisons herself by tasting her own poison and dies. The hero knows she's an assassin and watches her sneak into his room at night to kill him, only for her to bump her head.