Day 3: 4:00 A.M.-5:00 A.M. - S3-E16
Continuity mistake: When Michelle shoots the escaping hotel customer, her gun shows a jammed shell casing while she points her gun at him. The jammed casing wasn't there after she fired her final warning shots and disapears suddenly just before she shoots him down. (00:39:00)
Answer: According to Jack in season 5, Nina was "deep cover" before the pair ever met, so it's safe to assume she was recruited before she joined CTU. As for what her primary mission was, who knows? Perhaps it was to gather sensitive intel and pass it on to her superiors. Given that she worked for an intelligence agency, it's not a stretch. Or perhaps we may find out in season seven.
Cubs Fan ★