S.G.
I used to be scared of Scooby Doo when I was a child. I still don't watch it - (not that I would be scare:). My son got scared at Halloween (I think) 2008 and it lasted for a long while. He was so scared of going to use the bathroom or playing downstairs by himself or just going to bed. At one point I had to lie beside him until he fell asleep (talk about a waste of my evenings). He is much better now (almost back to normal) but I still leave the light on next door his room until I know he is in deep sleep. I also let him know he can come over to our room when he wants and he does.
She might get over it sooner. Would it help if she had some relaxing music while she tries to fall asleep? Just keep assuring her that you are close by and nothing can hurt her. Stay away from even fairytales with whitches as she might be scared without you realizing. Also she is that age where she better understands danger and also has wild imagination.