...it seems okay (granted, I only looked at the first two chapters). I do have a couple of issues with it, mainly relating to the use of "Danger" as a name the OC answers to. Who answers to "Danger" in a normal life like the one she presumably had before the fic began? The prophecy thing could also be a problem if she misplays it. However, she seems to have thought this through rather well. Not my cup of cocoa, storyline-wise, but well-written.
Grammar and spelling are exemplary, though; I didn't see a single mistake in the first two chapters.
If you're wondering if she needs PPCing, probably not. It's a pretty well-written AU and the grammar and spelling issues are non-issues with this one.