She was most likely groomed to threaten her parents. It is one of the first steps for a groomer - gain the trust, isolate them mentally, teach then to keep secrets and cover tracks and finally, to distrust/lie/blackmail the parents. After that point, many kids do what they want, they know they can get away with it, they do what they want at school too as the behaviour will propagate. Eventually this can/will result in child trafficking where the groomer will try to organise a real life meetup, often using catfish/faked details, rental cars etc to traffic the child from one point to another, and then another and then the kid is lost in the underworld and we might see it in the local news.
All cause the parent thought it was "cute" that their daughter/son has an instagram/snapchat/etc account. I think parents deep down knows what is going on but cannot face that reality. Or the parents live vicariously through them, trying to relive that self-discovery process as they monitor the devices.