She was married to actor Chris Messina from 1995 to 2006.She married actor Ron Livingston, her co-star in Standoff, on November 2, 2009, in San Francisco.
She is very much committed in the relationship with her husband and does not have any extra marital affair or has a boyfriend.
There is no such news about her getting a divorce from her husband.
De Witt played Emily Lehman in the Fox television series Standoff (2006–07), co-starring with her future husband Ron Livingston, as well as Charmaine Craine on United States of Tara.
She also was the title character in 2008's Rachel Getting Married, garnering several awards and nominations for best supporting actress.
She was raised in Hanover Township, New Jersey and she graduated from Whippany Park High School.
She also used to perform in many high school productions.Satellite Award for Best Supporting Actress – Motion Picture Toronto Film Critics Association Award for Best Supporting Actress Utah Film Critics Association Award for Best Supporting Actress Vancouver Film Critics Circle Award for Best Supporting Actress Washington D. Rosemarie Braddock Dewitt who is also known as Rosemarie Dewitt is one of the most popular American actresses.From May 4–23, 2010, De Witt appeared in MCC Theater's Off Broadway play Family Week, written by Beth Henley and directed by Jonathan Demme.In its review of the play, the New York Times stated that De Witt's lead performance "has many affecting moments as the beleaguered Claire." De Witt appeared in Showtime's series United States of Tara as Tara's sister, Charmaine., Damien Chazelle’s musical film set in contemporary Los Angeles and starring Ryan Gosling as a jazz pianist and Emma Stone as the aspiring actress he falls in love with.