I would agree with maybe asking more questions and trying to dig a little deeper, but if she doesn't show any disturbing behaviors, I wouldn't worry too much.
First, it's developmentally appropriate for that age (actually starting at 7) to be interested in death and some gore. The concept of death itself is hard to understand, especially for kids who haven't really experienced it themselves.
Second, I would say, just like some girls like pink princessyness, no matter how many cars you give them, some people just like that darker side more. Is it strange for a little girl to choose black over pink as the motivating color?
My own DD8, has stated black as her favorite color since she was 2! And at that age would rebuff pink pastel clothing and pull black out of her dresser. Her first favorite move was Nightmare Before CHristmas and last year, she wrote in her school journal that the wolf was her favorite animal because it would eat all the other kids favorite animals. She also wrote that her favorite place to visit was the Boston graveyards and she didn't seem disturbed (more like fascinated) with the child headstones...am I worried? Not a bit! She's sweet and kind and loves animals.
