Girl Gets Freaked Out by Her Sister Sleepwalking

This is something out of a horror movie.  A girl wakes up to her sister standing next to her bed just staring at her like a zombie. The frighten girl keeps shouting and calling her sister's name, but she doesn't even flinch. Her sister is sleepwalking and it goes on for almost a minute The freaky event finally ends when their mom comes in the room. One rub of the shoulder and the sister snaps out of it and lies back down.