Chao's a mage! Besides how would you differentiate a regular human from a "mage". From my view anyone can be a mage with the proper training (ex: Yue- She wasn't a mage before but now she can cast spells without the help of her artifact card).
Chao enherritted the blood of the Springfields I doubt someone from such lineage would not be a mage. It's just that her affinity is fire and that there are tatoos on her body. Also she has her own incantations which are used by mages everytime they had to cast spells. I deduce that the magical patterns on her body are just tools to magnify her magic since she's probably only a beginner at it. I don't believe that there's such as a fake mage... if you can use magic then your a mage how can anybody take that away from you and call you a fake. It's just that Chao's spells takes a lot from her and she's just not used to it yet just like how Negi was the first time she used Dark Evangel's dark magic.