Ghosts upstairs

My daughter is afraid to upstairs by herself at night. She states that there are ghosts up there and has gone so far as to name the 3 ghosts that reside in our upstairs rooms. So, to do anything that requires going upstairs, she needs an escort to ensure her safety. She sometimes takes the dog with her, but the dog is not always cooperative with her request, so, she relies on the protection of her 8 year old sister. She is very adamant about not going upstairs alone. So, for our amusement, as she is walking upstairs, we will look behind her and yell "look out!!!!" I know it's mean, but if you could see her face as she screams, it makes up for all the difficulties she puts us through!