Darla is the niece of Philip Sherman, a dentist. She is not antagonistic through evil or malicious intent but rather through rambunctiousness and the overexcitement of having pet fish, which ironically has frequently resulted in her killing them by accident.
Gill and the other fishes in Sherman's fish tank describe Darla as a fish killer and that Nemo is supposed to be her new pet fish. The last fish she received, Chuckles, was killed by her because she wouldn't stop shaking the bag Chuckles was in. In the scene where Darla is about to take Nemo from her uncle, Nemo plays dead, but Darla thinks he is just sleeping and starts shaking the bag. Gill then fires himself out of the tank and lands in her hair, causing her to drop Nemo bursting his bag. After Gill catapults Nemo into the air, Darla tries to grab him, but he lands in the sink and is swallowed into the drain leading to the ocean. Darla then looks down the drain and screams, "FISHY!" The drain squirts water in her face as she breaks it. It is unknown what happens to Darla afterward.
Toy Story 3
Darla Sherman was seen in the magazine that Molly Davis read after organize her donations to Sunnyside Daycare in Toy Story 3.
Darla's photo that her uncle Philip Sherman have in his consulting office, appear in the Marine Life Institute in Finding Dory.
Darla appears in some Finding Nemo related attractions such as the Finding Nemo: The Musical show at Disney's Animal Kingdom playing the same part she did in the film, and in the Finding Nemo Submarine Voyage attraction in the lagoon diving with her uncle.