I would very much like to know the answer to this as well. I even talked to her after attacking some of the enemies (I think). After clearing the rest I went back and she was randomly dead, I swear I never hurt her, and I even kept the spiders locked up despite befriending them to keep them from harming her specifically. I tried to speak with dead to ask who killed her but there is no option for the question.
I do not want to have to redo all of the goblin fortress but I will do so to keep her alive, if I have to, if I can... I am invested dammit, but I need to know if it is even possible...
