She was played by Dora Madison.
Tilda was introduced as a college student and the best friend of the episode's main protagonist, Natalie, who was revealed as a call girl. However, it was later revealed that Tilda is running a prostitution ring with ties to the Russian mob, who set up Natalie with a rich businessman.
Natalie wanted to get out of the business as she had met and fallen in love with T.J. Blake, a Petty Officer. With Natalie's romance serving as a threat, the evil Tilda enlisted Benton, a security guard, to kill Blake--with the murder committed during a college party. She also made an attempt at Natalie herself, as she nearly ran her over in a SUV.
Tilda was revealed as a villainess in the episode's climax, when Natalie informed Tilda that Benton was arrested. Tilda firmly clutched Natalie and demanded to know what she told them, and it was there that Natalie realized that Tilda was running the ring. The villainess informed Natalie (in so many words) that her romance with Blake forced the Russians to put pressure on her, prompting the order to kill Blake. However, Natalie showed Tilda that she was wearing a wire, and following this, Pride and his NCIS crew entered the room and arrested Tilda, who called Natalie a "stupid bitch."