Well as the girl walks past the end of the hall way, you in fact don't really need her to even enter a door. Just place the door our of the players site (in the direction she has walked) and then destroy the girl at the end of her path (of course out of the players sight) near the door.
In the end the player see's her cross the hall way he/she is walking up and will of course turn the way she walked on getting to the end of the hallway. Will see the door and guess the girl entered it, maybe a little triggered sound of a girl crying/dying as the player approaches?
Then make your blood seep at the same time.