I would visit with the parents of the BF, see if they are ok and everything is legit. If you feel she might not be safe go the legal rout and bring her back.
^ False
Your accounts are your accounts. If there is information stored on that computer that is not protected in some way then you can legally access it. If there is any information either on the computer or on the web that is protected by a password you will be doing something illegal if you try to access it by force or without permission.
My cousin went to NYC like 3 months ago and told her mom she was going to rochester. After finding out that she wasn’t in fact in rochester, we tried calling the phone companies to track her through the GPS and they told us they wouldn’t do it. You can try, we just kept calling and asking and eventually they tracked it for us.