^^ Legally, but not realistically. I was certainly capable of giving consent when I was 15 (and did, actually, though she was only about two years older). My point was that being highly motivated to do something does not equal impaired judgment-- it just equals enthusiasm.
As I said earlier, the law was set at 16. You can make the argument for lowering it, but right now it's still 16. That makes the women in these cases rapists whether they think they are or not.
I believe it is not legally defined as rape unless the child is under 13. If the child is over 13 and under 16 it is a different offence of Sexual Activity With A Child.