That Graendal fled as soon as Rand's messenger came to her (though I find it quite unlikely, that she would already feel that threatened then, but rather see that as an opportunity). But I don't see her anticipating that Rand planed to balefire her palace and use Graendal's Compulsion on the messenger to prove that Graendal died. That's IMO simply too far-fetched, especially since Graendal could then simply refuse to use Compulsion on the messenger and Rand would have thought that Graendal isn't in this palace at all.

Besides, as you concede in a post above as well, the timing of Graendal's death near the end of the series indicates that RJ simply wanted to resolve her plotline.