Rabe was born in New York City on the Upper West Side, the daughter of playwright David Rabe and actress Jill Clayburgh (1944–2010). She has a younger brother, Michael, an actor and playwright, and an older paternal half-brother, Jason, a musician. Her father is Catholic, her maternal grandfather was Jewish, and her maternal grandmother was Protestant. Rabe was raised in Bedford, and moved to Lakeville, Connecticut when she was in the seventh grade. There, she attended the Hotchkiss School.\n', '
Rabe studied dance for ten years. She was teaching ballet at a summer arts program in Connecticut, when she was approached by the program\'s acting instructor, who asked her to perform a monologue in the final production. Rabe performed a monologue from the play Crimes of the Heart by Beth Henley. She stated, "It was that moment, performing that monologue, that made me think, \'Maybe this is what I wanna do\'." Rabe then went on to study acting at Northwestern University, from which she graduated in 2004.\n', '
In 2001, Rabe made her screen debut opposite her mother Jill Clayburgh in the film Never Again. In 2002, Rabe made her professional stage debut, again opposite her mother, at the Gloucester Stage Company in Massachusetts. She starred in two one-act plays: Speaking Well of the Dead by Israel Horovitz, and The Crazy Girl by Frank Pugliese. As a result of appearing in the plays, Rabe was able to get an Equity Card. In July 2003, Rabe returned to the Gloucester Stage Company to appear in a production of Proof by David Auburn. The same year, she appeared in the film Mona Lisa Smile. After graduating, Rabe moved back to New York. From September 29 through October 2, 2004, she appeared in White Jesus by Deirdre O\'Connor, one of a series of one-act plays presented as The Democracy Project from the Naked Angels Theater Company.\n', '