Kristen was born in Brooklyn, New York. She made her screen debut in the female lead role in the 1971 comedy film Preacherman. Having acted off and on Broadway for several years, including the musicals Grease and Mayor, Kristen made her television debut in the role of Delia Ryan on the ABC daytime soap opera Ryan's Hope in 1975 and remained with the show until 1979. In January 1982, she returned to television, portraying Georgina Whitman on One Life to Live for a few months before being asked back to Ryan's Hope in March 1982 where she remained for a year and a half. She returned to Ryan's Hope in 1986, remaining there until it was cancelled three years later.

After Ryan's Hope, she joined the cast of ABC soap opera Loving from 1990 to 1991, playing the role of scatterbrained Norma Gilpin, and in 1995 had a role on Another World as the alcoholic Madeline Thompson, before she signed on for the role as neglectful mother and later beautician Roxy Balsom Holden in One Life to Live in 2001 where she appeared until its final episode in 2012. Kristen was nominated for two consecutive Daytime Emmy Awards in 2004 and 2005 in the Outstanding Supporting Actress in a Drama Series category for her role in One Life to Live.

Kristen guest-starred in the number of television shows, including Law & Order, The Sopranos, Law & Order: Special Victims Unit, and Unforgettable. In the fall of 2013, she appeared on General Hospital reprising her old role of Delia Ryan from Ryan's Hope who was revealed to be Ava Jerome's natural mother, and has made periodic appearances as the storyline has dictated.