Wow. I don't want to be out of line here or anything. But there is a definate reason for this behaviour, and underlying issue. Kids/teenagers don't just act out like this for no reason kwim? I hate to ask but has there ever been any kinds of abuse? Or someone she was extremely close to die or something like that? Or does she have issues with your mum's partner? Thats where your mum needs to start I think. Finding out what the underlying problem is, because this just goes way beyond a kid just "acting up" kwim?