It's okay, she is only half demon. They explicitly made that distinction this chapter and also showed she was in control of her wits and will. She even self-destructed when she realized it was Vikir she was fighting, not that she would've survived facing him without that mistake.

Vikir will realize something as she mumbles about him and their past and stops his blade. As to how they can remove the demon from inside of her, he will just have to hunt down the one who gave her powers.