Is it normal for a girl stalking a boy at school?

There is a girl in my 14 years old cousins school which doesn't leave him alone for a moment. She follows him in the school yard during brakes and all the way to his house after school. He is really annoyed by her and has repeatedly told her he isn't interested in her (and even threatened to punch her) , however she persists stalking him all day long. Even more, two weeks ago he told me she even tried to tuch his.....you know what. I don't know if that's true or he's exaggerating because he can't stand the situation any longer and wants to put an end to it. Poor guy, he's even ashamed to tell his mum about it. Also she's 2 years older. So is this a common thing between teenagers at schools or we need to do something about it?