After revealing her identity, she confiscates Elizabeta's cocaine, and naturally, she and Niko break up.
Despite her intentions, it appears as though Karen genuinely fell for Niko during their time together.
Michael and Franklin Clinton start opening fire on the agents, but Karen manages to escape unharmed and calls for back-up.
Nevertheless, Michael gets away with the Azerbaijani prisoner and she is not seen again for the rest of the main storyline.
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.
She apologizes to Niko for lying to him and says that he is a "nice guy" who is "better than the creeps [she] normally date[s]", indicating that she took a liking to Niko even though she was only supposed to spy on him.
After she takes Niko to the United Liberty Paper Contact's office, she is never seen again for the rest of the game.
She is also visibly hurt when she is forced to betray him, and upset when Niko calls her a "fucking bitch." After this, she is seen outside the United Liberty Paper building in Algonquin smoking a cigarette.
During a mission for ULPC, Niko asked what Karen's reward for bringing in Niko was, to which he replies "We gave her life back", once again hinting towards a previous criminal affiliation.
Five years after the events of GTA IV, it is revealed that Karen is now a high-ranked IAA agent.
After receiving confirmation from the IAA that the crew is legitimate, she prepares to hand the code to the crew leader, but when she puts down the briefcase containing the access code, an FIB team ambushes the meeting and kills her bodyguard.
Karen immediately runs off while the crew starts killing FIB agents.