Ah, I see, I misinterpreted your wording above. Mother is not to blame - and you're right that a nearly-teenager should be allowed a certain amount of latitude, to earn further trust.

In which case, carry on as you were. Hopefully, Girl has learned a valuable lesson that the kindness of strangers can never, ever be taken for granted.

I do wonder how much you were a paragon of virtue at a similar age...