Why is my teenage sister without empathy?

She may be a sociopath: http://www.youtube.com/watch?v=Ha3XSeulqWY. This is a problem affecting over three million people world wide and there is not any real treatment for this. Only with relentless psychotherapy approaches has this condition ever improved. My ex girlfriend is a sociopath and i know this sounds a lot like her, ask her if she has feelings. Ask her if she believes she has a soul. If she becomes irritated at these questions I'm probably right. Does she start social relations with self conscious people to get things from them or seem to use them? If the answer is yes the answer is yes. Recommend her to a psychiatrist, she may not have a conscience get help or she will make life a living hell for everyone around her this is inevitable. Good luck it's very tough with this one, take her to church.