http://www.kids-in-mind.com is a pretty useful website that gives movies more detailed ratings than the standard MPAA system of G, PG, PG-13, and R. It has three different ratings on a scale of one to ten for Sex/Nudity, Violence/Gore, and Language (PotC is 3/5/3). Then it explains in detail exactly why it gave the numbers it did. Sometimes, in doing so, it gives away certain things about the movie. (For example, if it said “A woman is shot in the head and killed.” and there was only one female character, the surprise of her death would be spoiled.) I wouldn’t worry about spoilers for a Disney flick though.
I wouldn’t swear by that website, but it might help you. My personal opinion is (as someone said already) that it depends on the kid, because they’re all different. If she wants to see it, I guess I’d let her, but I’d make sure she had some idea of what she was getting into. Those skeletons could be a little scary.