Revealing mistake: Bad guy is shot but can be seen breathing afterwards on the ground. At the start of the next episode, he was shown to be shot in the head. (00:40:38)
Revealing mistake: When Dan is shot at the end, you can see protective equipment under his shirt as he falls back. (00:40:40)
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 ★