So at 15 you're still a child and can be easily influenced but, a few months later, at 16 you're not? My point is that yes she was legally a child but only legally. Whether or not we can actually class her as a child who is too young to have sex is a different topic that cealry different countries differ about.
I understand his point but there's a difference between a lack of law and differences of law. The fact that there are differences regarding the legal age to have sex is enough to highlight that it isn't objective and that she was actually a child.