Three things. You notify the other parents that she is a runaway and you want her returned home. Tell them if they do not do so, you will take whatever steps necessary to have them prosecuted for kidnapping. You then call the police and report her as a runaway and give them the address where she is staying. Third, you go to the juvenile court and you get a protective order concerning the adult boyfriend ordering him to stay away from your daughter.
Yo may also consider some disciplinary measures as well. If she has a cell phone, take it. If she has a driver's license, take it. If she has a computer, take it. If she has a bank account, take her bank card and check book. Change the locks on your doors and take the keys. As a minor, she has no property, she only has privileges to that which you give her. It matters not how she came into possession of it. She only has the luxury of it's use because you permit it. Let her know that a) you are the parent and she is the child (she's not an adult until she turns 18), b) she will follow the rules and if so you will consider returning privileges to the property you have confiscated.
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