A good guess, but that's not the reason. She and many in her group use Snapchat and Instagram (if I have those names right - I've never even opened a page, if they have pages, on one of these services) knowing that at least a handful of parents established accounts specifically to keep an eye on things. They don't care. They even happily interact with the parents on the platforms. They just don't like Facebook. When they want to have (what they think are) private conversations they use WhatsApp, etc.