Graendal already knew that Rand stays in Arad Doman. According to your view on Graendal, she already would have fled, when she learned that Rand is in Arad Doman. Graendal had to stay, though, to fulfill Moridin's orders. That the DR would eventually contact "Lady Basene", if he is in Arad Doman, must have been obvious to Graendal. Thus Rand's messenger certainly was in Graendal's view finally a nice opportunity to get a grip on Rand and accomplish her goal, not something that immediately scared Graendal so much that she left her Arad Doman, risking Moridin's anger.

Besides that, there is no obvious relevance for Graendal in the plot anymore. The other surviving Forsaken have at least logical confrontations open or are still a mystery, e.g. Moridin, Demandred and Cyndane with Rand, Moghedien with the Wondergirls, Aran'gar maybe with Perrin and of course Mesaana's & Demandred's identity. Graendal managed to create chaos in Arad Doman and Shara and the point of her death was to demonstrate that Rand has become more and more unhuman. She isn't needed anymore. It would be useless to still have Graendal around for the Last Battle in a new location, especially since she is a behind the scenes manipulator, not a general.