Williamson had previously auditioned for a role on OLTL but was rejected because of her resemblance to Actress Erin Torpey, who was playing Jessica Buchanan on the show at the time. When Torpey resigned in January 2003, Williamson was remembered by the casting department and offered the role of Jessica.
On December 29, 2005 Williamson married Josh Evans. In the July 3, 2007 edition of Soap Opera Digest, she announced that she and Evans had separated in June 2007; they later divorced. In the September 2006 issue of ABC Soaps in Depth, Williamson revealed she had just received her green card and proudly proclaimed, "Now you can't kick me out!"
In 2009, 2010 and 2011 Williamson was nominated for a Daytime Emmy Award for Outstanding Supporting Actress for the role of Jessica. In 2009, Williamson appeared as Brandeis on Gossip Girl in the episode "The Grandfather: Part II"; she reprised the role in the 2010 episode "The Empire Strikes Jack". In 2012, Williamson joined the cast of Haven as Dr. Claire Callahan for Season 3, which began airing in September 2012. In 2013, Williamson appeared in flashbacks as Vivian Banks, the murder victim in the NBC TV series Deception.
In 2006 Williamson was a co-host for the Planned Parenthood Awards, which honor individuals and organizations for "their contributions to protecting women's rights." She also appeared in a public Service announcement for breast cancer awareness. In 2008, Williamson married Michael Roberts. On September 21, 2010, Williamson and Roberts welcomed their first child, McGreggor Edward Roberts.
In 2015, Williamson appeared as April Littleton, a famous Photographer going back to her hometown, in Portrait of Love, which premiered on Hallmark Channel on March 7. On May 26, 2016, it was announced that Williamson would originate the role of Claudette Beaulieu on July 5, 2016, on General Hospital.
