How scary is too scary?

I started working on a young adult novel a couple of years ago and it is now down to the final 10 pages. In the past couple of months, I have submitted query after query. Everyone keeps saying the same thing: "It sounds very intriguing, but is not a right fit for us....Don't give up though. We're just one agent/publisher and there are many more." I realize that most first-time authors submit to dozens of publishers before they finally find one, but it does get frustrating. I keep wondering if something is wrong with my hook, maybe the wording is not catchy enough and I should change it....or maybe my book is just a little too creepy for young adult fiction?

It's pretty much about a teenager who sees a ghost. The ghost is the little sister of one of her friends. The reason for the little girl's death was unknown, she just got really sick one day. But, after seeing her, the teenager finds out there is so much more to the story and becomes entangled in several different stories involving her future and her mother's past. That's not exactly how the hook goes (don't want to give away too much), but it's the general idea. Every time I submit the query letters, I keep asking myself if I would want to read this book. Of course the answer is always yes, I mean I wrote it, so it's interesting to me. But, for some reason, even though this is a fiction story, the ghost or spirit seems more real than a vampire or zombie. I think that might be a problem, but not sure. Most ghost stories in young adult fiction, are meant to really scare the reader or in some cases they're really funny. In this story, however, everything is so realistic that the creepy vibe might seem a little intense. The book is about unlocking secrets and is more about adventure than anything, but the hook does make it sound creepy. I guess I should work on that.