In 2009, Schull had a guest star role on the Fox TV show, "Lie to Me" (season 1, episode 4). The same year, she was seen in the Lifetime Movie "Sorority Wars" starring Lucy Hale and Courtney Thorne-Smith. She also guest starred on The CW's "One Tree Hill" as Sara, the spirit and memory of the deceased wife of Clay (played by Robert Buckley), and also as Clay's wannabe lover who bears a striking resemblance to Sara—Katie Ryan. She guest starred in an episode of "Ghost Whisperer" (Greek Tragedy) in 2009, and episode 14 of "Bones", in 2010. Schull recurringly appeared as Meredith, who is Aria's (Lucy Hale's character) dad's former lover, in the ABC Family series "Pretty Little Liars". She also appeared in an episode of "Hawaii Five-0". In March 2012, she appeared in a McDonald's commercial for the Shamrock Shake and in April she guest starred in an episode of "Psych". Also in 2012 she appeared in an episode of "Grimm" as Lucinda, a character who resembles Cinderella, but with a twist. In February 2013 she appeared as Agent Naomi in an episode of "Nikita" (Black Badge). Since 2013, Schull has appeared in the recurring role of Katrina Bennett in USA Network's "Suits". In March 2018, she was promoted to series regular for the eighth season of "Suits".