i think you need to remember that Jenny (the docs daughter) never regenerated straight away and just because you see a gravestone it doesnt mean that the person is there.
Of course I know that, but as I clearly stated, I assumed that the Doctor, Vastra, et al. would've been involved in arranging her burial, and thus would have known if she had come back to life after a few hours like Jenny did. Granted, the Doctor didn't actually see her gravestone until it was already in place (since it was only then that he learned her full name), but I'd think the others would've been aware of her burial arrangements.
Besides, it's just so unimaginative to assume she's just something we've already seen. True, Moffat does return to the same wells rather often, but for now I'm willing to give him the benefit of the doubt and believe he's come up with something less obvious.