She is portrayed by Mia Kirshner.
On Day 1, Mandy was working for Ira Gaines. She got on board a plane with a photographer, Martin Belkin. She blew up the plane with a bomb, killing Martin. She worked with Bridgit to get Martin's ID card, but Bridgit asked Gaines for more money for the ID card. Gaines seemingly accepted the deal, but after transferring the money to Bridgit's account and receiving the ID from Bridgit, Gaines had his sniper, Jonathan Matijevich, shoot Bridgit. Gaines asked Mandy if she was interested in a job in the summer, to which she said that she was in order to avoid suffering Bridgit's fate. She left Gaines's hideout afterwards, and would no longer be involved in his plans, as he was killed later on that day.
In The Game, Max had her slit James Radford's throat when he tried to back out of his deal with Max. Mandy's employment with Max came to an end when Jack killed him aboard his yacht.
On Day 4, Mandy was hired by Habib Marwan as part of his terrorist plans. During his plan to kidnap and execute secretary of defense James Heller, she called him from his son Richard's cell phone and told him where Heller was going to be, while Richard was in bed with Mandy's partner, Gary. When it became clear CTU would be going after them, Mandy killed Gary, and then killed CTU agent Lee Castle and took Tony Almeida hostage. However, she was cornered by Jack Bauer and subdued by Curtis Manning, and was finally captured by CTU. In the interest of time, as Marwan had sent a nuclear warhead toward a location unknown (later revealed to be Los Angeles), Jack offered her a presidential pardon from President Charles Logan if she gave them Marwan's location. Mandy gave them Marwan's location and was granted immunity from her past crimes, including the attempted assassination of David Palmer.
Mandy has not appeared since. She was intended to appear in both Seasons 7 and 8, but the writers decided against it to avoid "sensational moves". It is likely, given how cautious she usually is, that she stopped working for terrorists to avoid being captured again, although this did not happen with Nina Myers.
She has, however, appeared in two books, one of which has Jack call her for help, and she takes his side rather than the Russians who hired her. It is unknown if these books are canon, however.