From the starting point (the front door) head left and then right into the kitchen.
Go through the kitchen to a backroom where you'll see Emily scurry across the floor behind some furniture.
Follow her behind and fall down the hole into the basement. Emily will then run at you and kill you and the trophy will pop.
Must be done before 4am and also must be done before you find the secret basement to the entrance in the master bedroom which unlocks: