General Anaesthetic..So nervous!?

My friend's daughter (13) is due to have a general anaesthetic soon (having two teeth extracted). This is just due to nerves! She wouldn't like to be awake during the process. The nurse told her the worse thing that can happen is you either don't wake up and can not be resuscitated or just don't wake up or you wake up during the procedure. What are the chances of this happening? Has this ever happened before? She is extremely nervous! She is scared that she won't wake up. Please help - and soon! Thanks x