At the Forsaken Garden Party in KoD, ch.3, Aran'gar muses regarding her possible alliance with Graendal:
"In truth, she had made several [alliances], but her allies always seemed to suffer fatal misfortunes once their usefulness ended, and they took all knowledge of the affiliations to their graves. Those who found graves."

Even if Aran'gar wasn't responsible for her death, this description would in hindsight perfectly foreshadow Graendal's demise in TGS:

Graendal and Aran'gar became allies, but obviously Graendal's usefulness ended after Rand appeared in Arad Doman, spoiled Graendal's plans and found her hiding place (one could say, her usefulness as a character in the story ended as well). Then Graendal suffered a fatal misfortune (especially that Nynaeve found Graendal's trail in time), which led to a balefire death without even a grave, where Graendal took all knowledge of the affiliations to Aran'gar with her.

Knowing that RJ liked to include such foreshadowing in the story, I think this further supports the apparent occurrence in TGS, namely that Graendal died her final death. It will be interesting to see if Aran'gar will think in the next book about the irony, that yet again one of her allies died under unfortunate circumstances, like she considered not so long ago in KoD.