Unfortunately best way to keep her alive is to persuade her to join and just use her two clicks of ice storm then leave her far away from everything.
This fight goes even worse if you try to use cloudkill or wall of fire, all the harpers go extra kamikaze into your AoE and die.
The thing that makes this fight hard is all the useless 'allies', I swear they are just there for fodder for the orc boss's black hole, and the enemy casters then cover you with evards tentacles.
An idea I just thought off is to prep thunderwave and just blast all the silly allies away if you can, the only one you need alive is Jaheira if you want to permanently recruit her later.
