K.W.
Halloween Haunt at Worlds of Fun is pretty mild. I think she would be fine. As for other haunted houses, it's up to you, but I think they're pretty scary, if for no other reason than they're in very old buildings and they're so dark. You could so easily get hurt in there. I also think the people that work in them are pretty weird, so I wouldn't let my kids go unless they were with one of their parents (not me, because I don't like them).