First, give her the opportunity to understand this beforehand. Talk to her rationally and inform her of the consequences that will follow if she doesn’t change. You have an obligation to protect her and keep her safe, not respecting her privacy. That does mean not only knowing who her friends are, but who she is communicating with online and what types of pictures and videos she’s viewing. It’s not that she cannot be trusted to make good decisions, but there are predators out there who will try to get access not only to her, but also you and your financial situation. Meaning, aside from the pedophiles, there are software programs that can be introduced to your network that are intended to capture passwords, banking details, and other confidential information. She might be smart enough to avoid the pedos, but is she smarter than the programmers, hackers and scammers too? Next, remembering that you’re the parent and set the rules, deal with the disobedience. If you cannot physically control her, then punish her other ways. Such as disconnect the cell service and changing the WiFi password. Yes, it will have an affect on how you manage life with her now but this is temporary. I say it’s temporary because everyone learns. What she’s learned so far is if she fits, she keeps her phone, and gets her way. Soon, she will learn how to behave in your household. She is 13, she needs to live within her boundaries and rules. That is what we expect from everyone in society.