Wendy Smith is the main villainess from "Switch," episode 3.05 of NCIS.
She was played by Merritt Wever.
Wendy Smith is the wife of Petty Officer Jerry Smith, who was killed while driving on Route 249. As she told Ziva and Gibbs during her interview at her home, Wendy and Jerry were practically newlyweds, as they were celebrating their six-month anniversary. As later revealed, though, Wendy's grieving demeanor masked her true persona: a bitter and scorned woman.
Wendy was unhappy in her marriage due to Jerry cheating on her constantly, even doing so on their wedding day. Jerry was also sleeping with the wife of Commander Morris, and that transgression was the last straw for Wendy. The villainess followed him out of the Norfolk Base, and after driving right next to her husband, Wendy pulled out a gun and fired shots at Jerry through the driver's side windshield. The shots went through Jerry's neck and caused him to crash his car, with the trauma from the crash killing him.
Wendy was revealed as the killer when Gibbs and Abby spotted part of a message written in blood. Jerry was trying to identify his killer, and what Abby thought was an "M" was actually a "W"--for Wendy. Gibbs returned to the home with Ziva to confront Wendy, who denied the claim, stating that she was at home talking to her husband. Though Jerry and Wendy were in communication and arguing on the day of the former's murder, Wendy was right behind him when they talked, as she had her home phone number forwarded to her cell. Wendy showed her true bitterness for her husband by revealing that he cheated on her on their wedding day, indirectly confessing to killing Jerry. She was later arrested (off-screen).