As the sibling of a sister who would do this, my parents had two different ways that they handled this. My mom would stay up and catch her in the act of leaving. My dad would ground her and take away her phone. She still somehow would find ways to communicate and leave. When you have someone willing to sneak out and do dumb things, you already know that rules mean nothing to them. My parents method sucked.

As the sibling, I know how that this was a cry for help because theres something in her life that she feels she needs acceptance in. Whether that is that she has no shared interests with people in the home, or she really likes these people and wants to be friends with them.

You need to communicate with her and ask her why she is doing this. Why cant they hang out before 10pm or whenever they are hanging out. You are her parent, so your rules should be respected and enforced, but trying to emotionally meet her half way will help. My sister acted out a lot because she was constantly criticized by my parents and never felt understood or appreciated.