Would bet my life on the fact that if Themis ever used her Sigil, which I assume is some kind of mind manipulation using their desires or something like that, it would not work on Kaname because his desires are too true and pure or some bullshit. I should say I'm a big fan of the manga as a whole, but her big Nani moment seems a bit predictable. That or she'll just fall in love with him and decide not to try it.