O'Reilly graduated from
Menlo School in 2003 and attended the
University of Southern California for one year before dropping out. After graduating, O'Reilly began her acting career in 2003 in the film,
Bill the Intern. She has appeared in several other movies like
Dinocroc,
Nancy Drew,
Just Add Water and
Forgetting Sarah Marshall. She also acted in television series like
CSI: NY,
Unhitched,
The Vampire Diaries and
Prime Suspect. In 2011, she appeared in the movie
The Help based on
Kathryn Stockett's best-selling novel
of the same name, a period piece set in Jackson, Mississippi, in the 1960s. The film opened to positive reviews and became a box-office success with a worldwide gross of $211,608,112. It also won several ensemble awards including
National Board of Review Award,
Screen Actors Guild Award and
Satellite Award. O'Reilly co-starred in the 2013 film
Jobs, alongside
Ashton Kutcher and
Josh Gad, about the life of technology pioneer
Steve Jobs. In 2016, she appeared in the
Roundabout Theatre Company off-Broadway production of
The Robber Bridegroom. A
cast recording featuring O'Reilly in her role as Rosamund was released on September 9, 2016. In 2017, O’Reilly starred as Sarah Foster in the film
Sleepwalker. ==Personal life==