Became known for her starring role as Ramona in the 2010 film adaptation of Ramona and Beezus. She has also appeared in such films as The Conjuring, Reign Over Me, White House Down and Crazy, Stupid, Love. In 2014, she began playing the character Greta Grimly on the FX series Fargo.
She starred in over 100 commercials after getting her first job as a model for the cereal Life.
She made a brief appearance in Taylor Swift's music video "Mean." She provided her voice for the film Ice Age: Dawn of the Dinosaurs.
Her sisters are actresses Hunter and Kelli King. She has been in a relationship with actor Jacob Elordi.
She played a young version of Marion Cotillard's character in The Dark Knight Rises.