oh my gosh i feel soo bad for her!! life is so cruel when your that age and especially when your own friend is the one that is bullying you around.. my mum used to step in with me and i used to just stay behind but it became more frequent till i did something myself in which was a massive explosion maybe tell your daughter to remove herself from that person for abit and if it keeps up maybe then you will have to alert her school authorities as this is definently a form of bullying which i understand is not tolerated... i hope she is ok the poor girl