Thanks for your comments, Myriad. I have made a small change to the containment procedures, and have removed a little bit of extraneous detail from the autopsy reports at this stage.
I'm very pleased that you worked out what she is - I wasn't sure how clear that would be, and I couldn't believe that there wasn't already one on the site (that I could find…). And I hadn't really thought about the significance of a tanner in that context, for the reason below, but that's quite a neat coincidence.
To your main concern: the truth is, I didn't really have a logical connection between her main anomalous effect and her identity. The tradition doesn't seem to have an equivalent effect, and I needed something so (a) the Foundation would pick her up; and (b) I could indulge in some body-horror. And I had imagined her as being based on the legends, but actually being an extra-dimensional being that had followed a similar course. Hence the stolen item isn't necessarily skin - it's simply something extra-dimensionally relevant (perhaps even a dimensional-travel item).
But I can see how the gap between anomalous effect and identity might bother a reader. My first attempt at a solution is to note that she herself has anomalously shaped organs, but that they don't move. Do you think that's enough to sell the "not from this world" angle, and enough of a link?
Anyone else care to share feedback please?