At the beginning of Dragon's Eye my characters can't enter the dungeon. At the entrance my characters can talk to Izbelah but she never attacks, and I've tried killing her but she just keeps taking damage without dying. I don't want to give up on the game after spending so much time on it - any suggestions?

Revert from previous save. If you dont have a specific save in Kuldahar then you will have to work from the previous Chapter save.
The entire Dragon's Eye area is littered with bugs. Even if you manage to MoveToArea, the Izbelah bug will interfere with the mandrake potion episode.