Lilith stood coldly as she silently calmed herself. She could not very well tell a fanatic like Balthasar the truth. Because to do so would lend credence to Zane's claims that their mother favored him. To put it simply, there was no physical way that Zane could have possibly broken through her charm.
It was a mental ability that Lilith possessed. She could quite forcibly bind weaker beings to her will and permanently at that with a simple gesture. It was a skill that among all the Horde Kings only she possessed. And even those of greater strength would have a hard time overcoming it. Except for Death herself, of course.