Another possibility is that Graendal used a similar weave on the messenger that Sammael previously did i.e. a messenger who could respond to Rand's reply. In Sammael's case the messenger died, and Sammael was aware of Rand's refusal to sign a truce. Graendal's may be similar because the messenger looked terrified when Rand suggested finishing off Graendal.

Just a possibility I guess.

Still, I read the chapter again and I think she is dead. The riddle was how to defeat someone who is cleverer than you. He says she'll suspect anything that he tries, and it will fail - he can't get her to duel him, and she'll flee easily. The solution is to make her think you're playing along and then punch her in the face, which is what he did.

I honestly don't think she expected him to balefire the whole palace.