1 - It might be valuable to them if you watched them play a little bit before you spoke. Then you could speak specifically about things you needed to be tightened up that would get called in a game.
2 - Walk them through what I call "road game" scenarios. Tweet I blow the whistle, I call a foul that the player doesn't feel they commited. Now what is the proper way to ask and what isn't? I respond (explain the response in various cases). After the explanation player disagrees not believing they actually did what you are calling/accusing them of? Now what is the proper way to respond and what isn't? I respond (explain the responses in various cases).
3 - If your brave you may want to explain (especially to the young women and any of their parents watching) that contact is not foul. Go over something that happen in a game that are likely play on situations and things that you would be calling fouls.