My first instinct on reading that scene was that Graendal was about to be tortured and killed by the fade for his amusement, the way captured Borderland women supposedly are. A mindtrap makes sense, but I'm still inclined towards her being dead. Graendal's only two talents are Compulsion and Screwing Up, she's killed more Forsaken than basically anybody except Rand, and she's more a liability to the Shadow than an asset. Moridin can't keep pulling cour'souvras and all these other AoL goodies out of his hat forever, so logically he must have a limited supply. Better to kill Graendal and save the cour'souvra for somebody who might actually be worth it.