'Ce' does not refer to a specific person or thing. It usually translates to 'that.' If you want to say she is not a child you would say: Elle n'est pas un enfant.
Can someone please explain why it's "Ce n'est pas un enfant" and not "Ce n'est pas d'enfant"?
I attempted to use infant and it was rejected. Is there another word that clarifies infant from child? Child=enfant, infant=?