I Became a Demon Slayer in Ancient Times

What does it have to do with her when others kill demons? She is just one of them, but why does she become a demon slayer when she wakes up again? When someone else travels through time, whether she is a legitimate daughter, a concubine, a doctor, or a peasant girl, she has a serious identity. How come she becomes a demon slayer? Will God let her live until the end of the play? No, she couldn't accept her fate and had to rely on her own hands and feet to make her own way.