observanteen
This is an important issue and unfortunately I know stories of young girls not much older than her that lost their innocence. I think you should speak to someone experienced for guidance with this matter.
Considering that this girl made you aware of the situation and keeps bringing it up I think its a sign from Shomayim giving you an opportunity to get involved in this and possibly saving her future.
How much are you responsible to do? I have no idea and Im not qualified to answer, but I think that you must do something (more than just asking our opinion).