User blog comment:KillRoy231/Gaines telling Jack to kill Nina/@comment-1474707-20180215175418

I think given his actions, Gaines could not have known about Nina's involvement with the Drazens.

My personal interpretation of Day 1's events is that initially, Nina's only job for the Drazens was to recruit a mole in CTU, which they then passed onto Gaines as a contact and he never knew how she was recruited. The reason Nina killed her just before she confessed was to protect herself, and then later the Drazens made Nina do more stuff (possibly by threatening to expose her if she didn't help them). This is all fan theory, but that's how I make it work in my head.

Kudos for revisiting Season 1! It's always been the best in my opinion :)