Towards the end of the episode when Nina's passport is flashed onto the screen and Kim reacts to it you can see that it shows an alias. The name on the passport is Sarah Berkeley, Sarah Clarke's married name now that she is with 24 (2001) alum Xander Berkeley.
The trivia item below may give away important plot points.
Vanessa Ferlito stated in an interview that Claudia and Jack were supposed to have a future together, but the writers had to kill her off when she chose to sign on to the Tommy Lee Jones comedy, Cheer Up (released in theaters as Man of the House (2005)). She felt this was a golden opportunity, since the producers at 24 (2001) never signed her to a long term contract.