Presumably sexually active 14 and 15-year-olds are having relationships with other 14 and 15-year-olds. This situation is really different.
I don't know; I think it varies. Often, the boy/man is older, I think. But I don't know by how much.
The question is not about the grossness of it. It's completely gross. But given how happy she was in the relationship, I'm not sure we should prosecute cases like that.