Human...? I'm sorry, I'm at a loss regarding her. Really, this isn't quite enough to go on, but there are a few things that help rule out possibilities. If it was a human being in control of some incarnation of death... Chances are that this version of 'death' was not some all powerful being. Which means I could likely safely rule out Azrael and Samael.

Thank goodness, of course, because I wouldn't wish to encounter either of them if I were you.

[He taps his fingers rhythmically against the book he was holding, his face screwing up in a look of minor confusion, with maybe a hint of fear. There it was again, that funny feeling... Like something about this was really bothering him.]

Death is, after all, a rather terrifying figure...