DD 12 has good school friend who happens to be a boy, but her dad won't let her go to his house after school even though friend's dad is there supervising and they stay downstairs in the living room or kitchen. I have met the dad and been to the house and happy with the situation. Having googled a bit I've discovered that this kind of attitude is quite common but DD and I think it's silly; any ideas welcome on how to handle this please.
Quite common I'm sure he's worried that your DD is growing up too fast or that this boy is more than a friend, but since you've already checked the situation and you're happy with it I would insist that your daughter goes. Why should the gender of the friend affect whether your child hangs out with their friends?