She was active in New York City theater throughout the early 2000s, during which she appeared in such shows as Avery Crozier's Eat the Runt, Hunt Holman's Spanish Girl, A. R. Gurney's Sylvia and Simon Mendes da Costa's Losing Louis.
In 2005, Williamson was cast as the wife of James Van Der Beek in the CBS sitcom pilot Three, which was ultimately not picked up.
[3] In 2000, she appeared in Eat the Runt, a comedy by Avery Crozier about a job applicant's series of bizarre interviews at an art museum.
The New York Times reviewer Lawrence Van Gelder said the gimmick was novel, but in the end, "the cast has probably had more sustained fun than the audience".
[4] In the summer of 2001, Williamson again appeared in Eat the Runt at The American Place Theatre, this time without the constant role switching.
[10] Williamson, along with other female members of the cast, was praised by The New York Times theater critic Bruce Weber as "for lack of a better word, adorable", and appeared to be "having great fun while they wait for better jobs".
[14] From October to November 2003, Williamson played the title role in Sylvia, a comedy by A. R. Gurney, at Playhouse on the Green in Bridgeport, Connecticut.
[16][17] The show opened with a controversial scene in which the protagonist performs oral sex on Williamson's character while his six-year-old son hides under the bed.
The New York Times writer Charles Isherwood said Williamson was one of the stronger cast members, but added, "the actors cannot do much to freshen the coarse innuendoes or breathe life into the plot contrivances".
She also appeared as a jogger in the 2005 independent comedy drama film Duane Hopwood,[27] and provided voices for pedestrian characters in the 2004 video game Grand Theft Auto: San Andreas.
[36][37] Williamson portrayed Nora, the mother of Loren Tate (Brittany Underwood), on the 2012 TeenNick series Hollywood Heights.