Mallorie was born in Puerto Rico, later moving to South Bohan, Liberty City. She occasionally works as a dancer for Manny Escuela in South Bohan, as well as an employee for Roman at his taxi depot in Hove Beach. Mallorie has been arrested on two occasions: in 1998 for joyriding and in 2002 for being in possession of a controlled substance (marijuana).Roman's cousin, Niko, discovers that she is having an affair with Vladimir Glebov. Although Niko warns Vlad multiple times to stay away from her, Vlad blows off the threats. Eventually Roman sees Vlad's car parked outside of Mallorie's place and puts two and two together. Roman goes to Niko for support, but when Niko reveals that he had suspicions of the affair, it only makes Roman feel more upset and betrayed. Feeling bad about not informing Roman or doing more to stop the affair, Niko decides that it's time to deal with Vlad once and for all, and the cousins head to the Comrades Bar to put a final end to both Vlad and the affair. Although at the time Roman seems to want a peaceful solution to the problem and calls Niko a "hot headed chump" after he puts a bullet in Vlad's eye; later in the game he tells Mallorie that it was him, not Niko, that killed Vlad in a jealous fit of rage, and that Niko helped him dispose of the body. When Mallorie tells Niko this, he plays along and supports Roman's claim, and tells her that Roman is an "old school romantic". Later in the game, after Dimitri Rascalov has Roman's taxi depot and apartment destroyed, Mallorie's cousin allows Roman and Niko to stay at their flat in South Bohan. Mallorie introduces Niko to Manny Escuela and Elizabeta Torres. Later, Mallorie calls Niko to tell him that Roman was kidnapped, and Niko manages to rescue him. At the end of the game, she marries Roman at a church in Suffolk and reveals that she is pregnant. Ending

Every single encounter that Niko has with "Michelle" has a hint that she is trying to gain information from him. She will always ask Niko if he is seeing or involved with someone dangerous, will constantly say that she is a good listener and that Niko can tell her anything he wants. When Niko takes her to a bar, he will even mention while drunk, that he saw her putting something in his drink. Sometimes, after a random date with her, Niko, will say that "There is something strange about her", showing that Niko is suspicious about her behavior. After disclosing her true identity, it is revealed that Karen is a smoker. She is not seen drinking alcohol, though it is unknown if this is related to her job or as a lifestyle choice.Karen is a Caucasian woman, with a defined facial structure, a slim nose, a prominent chin, and dark brown hair typically styled in a bob cut. Her casual outfit sees her in a black leather jacket with a white undershirt, beige cargo pants, and high-heeled black boots. Her working outfit consists of a broken brown two-piece suit, with a blue shirt, necklace, and high-heels.