You mean twitter or Snapchat. Snapchat is a site children shouldn't post to at all IMO. Twitter do keep accounts on their servers after deletion due child sexual offenders' use. It's the chat/webcam sites thare the real worry. Often their servers are located overseas in countries where they can operate legally and information is unable to be retrieved. Then there is the whole problem of P2P and IRC.
As for Tiah's peers, it may have been reported they weren't forthcoming but that could be for their own protection. I think it may be an case of an online child predator. Our kids are so vulnerable; especially foster children such as Tiahleigh IMO. Tiah was crying out for any tiny bit of understanding and affection, I think, hence her reported 'acting out'. Poor little love.