daughter keeps running away from home and worrying me sick..?

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My 15 yr old defiant daughter has ran away from home to be with a boyfriend that has gotten her involved in drugs, skipping school, stealing cell phones to communicate with boyfriend, you name it. I have stopped her from seeing him, and she just is determined to see him. I am so worried that she is going to get herself into lots of trouble, then it's going to be beyond my capabilities to fix. She is a good girl going through a bad age and caught up with a bad boyfriend that's going to eventually hurt her or cause her to get hurt. She almost killed herself this last time while she was gone. They argue and fight when they are together and are obsessed w each other to the point to where they just can't focus on anything but each other. She has no friends left because of him, and has lost all interest in school and family. I am wanting to find a tracking device that is unnoticed by her that is small enough to hide in her purse, as she takes her purse everywhere. I just need some rest knowing that I at least will know her whereabouts in the event that she does decide to run away again.

Thank you and any positive advice is appreciated.