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Jacobs was born in Pittsburgh, Pennsylvania. Her mother, Martina Magenau Jacobs, was a Carnegie Mellon University director of alumni relations at the Heinz College. Her father, William F. Jacobs Jr., was an investment banker.She was raised in the Pittsburgh suburb of Mt. Lebanon. She is of French, German, Irish, and Scottish descent. Her family owned the Jackson Koehler Eagle Brewery, established in 1847 in Erie, Pennsylvania, where her grandfather, John Martin Magenau Jr., served as President and CEO until its closure in 1978.

Jacobs began studying acting at the age of eight, and attended acting classes on Saturdays at the Pittsburgh Playhouse while growing up.She performed with the Pittsburgh Public Theater, where she was a perennial contender in the Public's Shakespeare Monologue Contest, leading her to be cast as Titania in its production of A Midsummer Night's Dream. After graduating from Mt. Lebanon High School in 2000, Jacobs moved to New York City, New York to attend the Juilliard School, where she was a member of the Drama Division's Group 33. She graduated with a bachelor's degree in 2004.