J.K.
I would say sorry, no one is allowed in the pool unless their mom or dad is with them. Go home come back with mom or dad. Chances are they dont come back or if they do they dont stay long. I would never let my daughter just jump in someone else pool without asking them myself, and really, I wouldnt let her go unless she was invited unless is was a really close friend. People are so rude. You could also just say, Im sorry we are not having company right now, we can call you to play another day.