She was born in New York to London-born restaurateur Keith McNally and American-born Lynn Wagenknecht. She attended the Lycée Français de New York as a child and is a fluent French speaker.
She is best known for her appearances in the films Frances Ha, Before I Disappear and The Disappearance of Eleanor Rigby: Him. In 2014, she appeared in the second season of Netflix show House of Cards.
She was previously in a relationship with actor Jonah Hill, who she dated for seven months from 2013 to 2014.