In 2006, Allen was a guest star on House M.D. in the episode "All In", as Sarah, the mother of a sick 6-year-old boy. She was also a guest star in the season 2 episode of Criminal Minds "Open Season" as the victim of two serial killers and alongside Cynthia Nixon in the 2007 season premiere of Law & Order: SVU. She starred as Julia Mallory in the first season of the FX drama series Dirt. Her character was a Hollywood heroin addict. She also appeared as a former love interest of Major Owen Hunt on the ABC's Grey's Anatomy in 2009. Other recent projects include the thrillers Hysteria, From Within and The Collective, and Old Dogs with John Travolta and Robin Williams. She has played regular characters in two television series: Katie Nichols in Terriers in 2010 and Hannah Britten in Awake in 2012. 2014 portrayed Meg on the side of Eli Roth, Peter Stormare and Elizabeth Whitmere, in the British horror film Clown. She also portrayed Linda Kessler in the Drama thriller film Nanny Cam.