What Solaz said. If the Humans win, their goddess will make them do the extinction route. Afterwards the religious propaganda will paint the demon race as even more barbaric and cruel and then, some centuries later, as unintelligent animal like monsters, that ate babies and souls. It's rather easy for an immortal goddess with brainwashing magic at her disposal to do that. I just can't believe that female hero is that naive, even so she should know Earth's history to some extend. Ethnical cleanup is a thing.