Even if I thought she was innocent, I would have still used her in my defense.
COURT: "Asoka, why were you in the room with the nano-explosives?"
ASOKA: "I was following a lead provided to me by Barriss Offee. She had uncovered a rumor that the explosives were being housed at that location. Barriss can verify this. I'm innocent!"
If Asoaka thought Barriss was innocent, that would have motivated her even more to reveal this information.