Continuity mistake: In the 08:00 - 09:00 episode on DVD (and during the previous few hours) you see Kim Bauer's feet and she is wearing sandals with no socks. At 08:36 when Terri has just been taken from the room where they are being held captive you see a shot of Kim sitting down and you can see that she is wearing pink leather slipper style shoes and black socks.
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.
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