Mischa Barton is returning to television — for one episode, at least — with a guest spot on Law & Order: Special Victims Unit. But the former O.C. star is reportedly making life difficult for her new co-workers.

Sources tell Radar Online that Barton couldn’t get any of her lines memorized, forcing the crew to spend all day on her scene. “She only had seven lines, seven!” a source says.

“Each time she would mess up, she would forget her lines and Mariska (Hargitay) kept prompting her and saying, ‘It’s your line, Mischa.’”