Apparently they indeed just met once very few weeks or so in TAR. Probably they also had an agreement not to attack each other (though we know that Aran'gar eventually planned for Graendal's death). In any case, since both had obviously more urgent things on their minds in the last weeks (namely Graendal Rand & Arad Doman; Aran'gar likely a new task by SH) nothing indicates that they created an elaborate plan to kill Demandred & Co. or something else, especially since it is clear that they don't trust each other that well. Likely only Aran'gar will now profit by taking over Graendal's network; on the other hand she is without an ally again, which might force Aran'gar to act sooner against Rand or the fellow Forsaken.