This was a story I read when I was young, I remember it being a short story and in an anthology. It would have been floating around our house in the 90's but is probably much older.
I remember at first the girl is talking to her mum, begging to come home, the mum convinces the girl, one more night, then you'll be home with me.... That night, the creepy doctor lets himself into her room. He hypnotises her, convinced that we can only feel pain in the brain and once she is under his spell she will no longer feel pain unless he asks her too.
He gives her a blade, and gets her to cut her palm - success! Then he commands her to slit her own throat... She does so, whilst manically grinning, he watches her die and then realises he is somehow now locked in until morning with a grinning corpse.
This story truly terrified me at the time and I would love to find it again.