She brought a child ticket from a machine at the station it was checked by a conductor with no questions and on leaving the station after putting her ticket to open the barrier she was pulled aside by i can only assume a transport police person as she thought she was being arrested by the police !!None of us were present so we cannot judge whether her questioning was an "interrogation" or not. Presumably she was asked to show her ticket; a child ticket was produced; the person checking the ticket then sought out the information needed to take the matter forward.
She is 16 - well above the age of criminal responsibility. So what action do you feel would have been reasonable under the circumstances?