Send a PM to "Intelligence" on the WWP forum page -
www.WhyWeProtest.net. Intelligence is David Love, a former "patient" and then "counselor" at Narconon in Trois Rivieres, Ontario, Canada, who finally wised up to the scam he was helping to perpetrate and started working to get the place shut down. It was a long, difficult slog, but he was ultimately successful.
He is now aiming his prodigious firepower at Narconon Arrowhead, a NN facility in Oklahoma.
There is no one on this planet who knows more about the inner workings of Narconon, the legal issues surrounding it, and its incestuous ties to the Scientology cult. He's an incredibly busy, incredibly driven guy, but might have some time to advise you regarding this situation.
I'll say this with some confidence of its veracity (Caveat: I'm not a lawyer, but...): There is nothing that anyone signed, nothing that Law Enforcement has decreed, no promises made by anyone to anyone else, that can legally stop your son's friend from leaving if she wants to. There is nothing that can legally stop you from speaking with her privately, if that's what she wants. There is nothing to legally prevent you from taking her home, if that's what she wants.
Do NOT lose hope. You're in the right. Narconon is in the wrong.
Good luck...