She has also had roles in the films Push (2009) as Teresa Stowe, and Leaves of Grass (2010) as Rabbi Renannah Zimmerman. She starred in indie film A Woman, a Part (2016) and had a minor role in the drama film One Percent More Humid (2017). She is the television spokesperson for the robo-advisor service Betterment.
Born to a father of Ashkenazi Jewish descent who was also a stage actor, Siff has stated that she feels “culturally Jewish because of how and where I grew up."[8][9]
She has appeared in such films as Then She Found Me (2007) as Lily, Push as a psychic surgeon (called a Stitch) named Teresa Stowe, sent to help Nick (played by Chris Evans), Funny People (2009) as Rachel, Leaves of Grass (2010) as Rabbi Renannah Zimmerman, and Concussion (2013) as Sam Bennet. She appears in the 2016 Showtime series Billions. She starred in an independent indie film called A Woman, A Part (2016) as well as One Percent More Humid (2017).
In 2017, she narrated the audio book Gwendy's Button Box by Stephen King and Richard Chizmar.
Starting in 2018, she has been serving as the television spokesperson for Betterment, an online investment service.
In 2020, Siff provided the voice for the titular subject of "Polly Platt: The Invisible Woman", over the course of a season of Karina Longworth’s film history podcast You Must Remember This.
Personal life
In October 2013, Siff announced that she was expecting her first child with husband, Paul Ratliff, whom she married in 2012. Siff gave birth to a daughter, Lucy.[10] Siff's husband died in 2021 of brain cancer.[11]