I agree.We know too much about Janis for her to suddenly be "revealed" as evil. She's humoring Simon in hopes that he'll tell her more secrets. After all, she and Simon have been trying to outmaneuvre each other for weeks.
Vogel is really the one with the suspicious background. When the warlord goes bersek, Vogel shoots his down while everybody else is still offguard. Because he wanted to shoot him anyway? And why would he tell X that "Mark Benford is dead" before the family is informed, unless they wanted him dead?
This is what I was thinking and am really hoping is true. If she really is the mole, then this show just tanked. In my opinion, when creating a mole character, (s)he needs to be a person who is dependable and pretty likeable, but stern enough that when they show their true colors, you can sort of believe it. Janis on the other hand has been like a cute cuddly teddy bear through out the entire show, and if she suddenly turns out to be the mole, I would be completely gutted
When making a mole character, one has to make sure that the mole isn't too likable because fans will hate you for it. Fans spend their emotional resources getting attached to a character only for you to say that it was all a lie? yeah, fans don't like that.
On the flip-side, it's a lot simpler to change an evil character into a good one because everyone likes a good guy, and we aren't all that emotionally invested in bad guys. Take for instance Juliet's transformation in LOST.