Meteor Swarm only does Bludgeoning damage on a direct hit. Seeing as it would be targeting the nearest unauthorized creature (a PC)...
Uttercold Energy Sub Meteor Swarm works, though given the way energy resist works with it it's more for healing her, and any other undead with cold immunity than hurting the PCs. Power Word Kill is also good. However I'm pretending Game Disjunction doesn't exist for reasons that should be obvious. Hm... Not Necromancy, Evocation, or Enchantment... Preferably no save, since it uses item based DCs which suck horribly. Metamagiced Summon Undead, perhaps? Though Summon Undead is capped at 5, and the results are non variable so Maximize and Empower don't help. Any ideas here?
The idea is that there are four of these, and they cycle so there's a Mass Harm every round, an Uttercold Meteor Swarm every round, a PW: Kill every round, and the other thing every round. Well, fifth round they all repair, and barring delayed activation there's nothing that can be done about that.