Right now it seems as if she never casts it. She keeps calling out her minion but it doesn't enter the game after a certain point. And it is after she kills her minions that she bumps up her aura. I tried going the distance with her tonight and the highest aura she ever used was 60%. Her minions stopped coming when she called them after that. It is listed on the wiki as "broken" so perhaps it is something that needs looking into.