Kim Raver was working on another show called "The Nine" when "24" started filming Season 6. Her contract with ABC said she would also be allowed to film some episodes of "24" later. However, "The Nine" didn't last long so that freed her up to return to "24" as soon as the powers that be decide to bring the character back.
However, given what I already know about this season, I would say the odds are better than 50-50 that Audrey will bite it but @ this time I do not know her ultimate fate. I have not yet heard of Kim Raver filming any episodes yet.
Oh, I kind of liked her, in a way. It seemed she was kind of realizing just who this "desk job guy" she fell in love with really was in season 5, and starting to love him for/despite it. And they seemed so in love before his "cruise" that you'd think they would need her for continuity before she meets her untimely end. LOL.