Pilar is Lawful Evil, operative word Lawful.
Her curse trusted her with this. She can do whatever she wants to serve Lord Asmodeus's interests, but she has to not do horrible things from the perspective of Chaotic Good, using her curse's power and knowledge, in the course of that.
Her curse wouldn't have steered her into the trap, obviously. That wouldn't have been nice either. But her curse could have just let the whole thing fly by without Pilar noticing.