Hou Yiwei is now under a lot of pressure because a newcomer managed to outshine him when they tried attacking the dark god with their god slaying weapon. He did not want to admit it but the woman that wielded another god slaying weapon is more proficient than him.
Given the fact that mages do not need mastery over their weapons is another reason, but Hou Yiwei does not accept that. He might lack in the pure power department, but he can attack much faster than her. He also noticed that the ever-spawning minions of the dark god did not target her much.
He also hated the fact that the Church of Light seemed to be favoring her compared to him in terms of support. He already knew how the Church of Light views the dragonkin even though they are already mixed in with human society.