She could have said:
“Why are you asking if God hath said? God did say this. Do you want to ask Him yourself? Wait and ask. Secondly, now why would God make a tree that does what He says it can do says and then want to keep me from it if all He had to do in the first place is never make that tree at all?”
Does “free will” ring a bell? That is the choice presented to all of us.
She could have but she hadn't experienced lies or deception before so that line of questioning could not have happen.