I killed her with a lot of shockwaves, and one mage with 2 rings of Will using MindDuel a LOT once her hp was down a little, and her morale was almost nonexistent. Gotta love lowering morale and hp, it makes Mindduel easier. I can't remember if I had to cheat to get 2 rings of will, but I only had the two.
Anyway, once she's dead, nothing special happens. Her summons go away, and the room goes to any normal room. If Erika is there, she wanders around like a normal townsperson. Erika will still die during the endgame. Funny happenings.
By the way, it took me 3 hours to kill Rentar, and a LOT of energy potion.