It would seem to me, to be quite unusual for a 17 year old female to be on an online dating site. Unless, she is part of a pre-planned scam attempt. Perhaps, coerced by someone else. If so, she may have “form” with other suitors on the dating site. I wonder if the Police have investigated the case from her side.
Have the Police pulled her Phone and Computers with regard to this case or interviewed her and her parents or guardian?
Do get suitable legal representation and good luck 🤞!