Yes, Nale the fool that he is, is nothing but a pawn in the hands of the IFCC. Sabine and Qarr are both higher up, but probably considered disposable. For Nale, who is nothing but a lowly mortal with delusions of grandeur, is almost certainly even more disposable to their plans. He's useful, but it's a finite usefulness, and I'm sure the fiends have plenty of mortals to fall back on should Nale get killed. But yes, I doubt Sabine even for a moment thinks Nale really has the upper hand over Tarquin, and she's not particularly cunning that I've ever noticed.