I get the feeling that for Xe'ra, she knew the prophecy and the pieces needed for it to happen, which she was following.
Thinking about the pieces themselves I'd say she didnt at all, seeing as how indiffrent she was to her subjects and so focused on how good illidan was, becuase of what he'd become, not exaclty becasue of what he had done.
Her reaction and cource of action when Illidan was hesitant and reluctant to submit sort of felt that way, she HAD to make the pieces fit, because thats the way the prophecy would come to fruition, it was like she couldnt compute it not following that path that had been laid out, hence her presistance and preachiness... and forcefulness.
though im just a dummy, but thats the impression i got when seeing the cinematic.