In the context of her possible alliance with Graendal that all her allies died (i.e. were actually killed by her), when they lost their usefulness,. This foreshadowing might not fit 100 %, namely that Aran'gar directly or indirectly killed Graendal, but I would say most foreshadowings aren't 100 % accurate (e.g. the Semirhage quote you mentioned also does state that Semirhage won't be sacrificed).

However, the quote still fits in an ironic way, namely that the author made Aran'gar's cynical thought actually come true: Aran'gar's new ally Graendal died lile every of her allies before at a time when she wasn't useful anymore in Arad Doman and in the story, misfortune actually played a part in it, and there isn't even a grave because of the balefire.