I've been watching season 1 of 24 for the third time, and trying to work out if Nina's behaviour does add up to the season's final plot twist.
This question pretty much explains everything: Why did Nina Myers help Jack Bauer if she was a mole?
However, in episode 22, while Jack is being held hostage by the Drazens and Chapelle refuses to do anything about it, Nina unexpectedly calls Palmer and asks him to help save Jack.
Now, I really see no reason for her doing that! She can just let things happen and continue to do her job, her employer's plans are succeeding and Jack's killing was part of it.
Is there any consistent explanation as to why she would go out of her way when she obviously didn't have to?