Battlestar Galactica (2004) (2004)

S1E7 Six Degrees of Separation

After a disagreement, Baltar finds himself deserted by the Number Six in his mind. To his surprise, she reappears on the Galactica, but this time she goes by Shelley Godfrey. Unlike before, she's visible to everyone and claims to possess proof from the deceased Dr. Amarak, which suggests that Baltar betrayed humanity to the Cylons.