Other mistake: When Jack sits down in room 2, his watch says 2:50, despite the time being 1:05. His watch is correct in other scenes so it's not that it's set wrong or broken. (00:05:00)
Visible crew/equipment: Just after Kevin is executed, you see the assassin walk off to screen left. However you see movement in the rear view mirror of the car on the far right hand side of the screen, evidently a crew member since everyone has been killed. (00:27:15)
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 ★