She was played by Virginia Williams.
Carla Shear is the attorney for John Vasile, who was, in actuality, Anton Zevlos--an infamous Romanian war criminal and human trafficker. It was also revealed that Carla was Zevlos/Vasile's illicit lover (Vasile was married to Maggie since escaping to Los Angeles), and she had known about his escape from Romania--though she was told by Zevlos that he was an arms dealer. She was first encountered by Callen and Hanna during their interview with Maggie, which ended with the pair uncovering Zevlos' secret room--which had weapons and other things connected to his old ties to Communist Romania.
Figuring that Callen and Hanna would get close to catching her lover, the evil Carla handed off Zevlos' Range Rover to a pair of teenagers as a distraction. Carla was taken to NCIS headquarters, where her affair with Zevlos/Vasile was uncovered during Deeks' interrogation. She was later informed of the entire truth about Zevlos, but the episode's climax saw Carla and Zevlos attempting to escape together on a yacht. Callen, Hanna, and Deeks caught up with the villainous couple, which led to Zevlos firing shots and even threatening to kill Carla. Hanna fired a shot to Zevlos' arm, allowing him to subdue and arrest Zevlos. Carla was also handcuffed and arrested by Deeks.