: I think you might've been led to that by preconception, because it seems to
: me that the appearance of the body is completely consistent with being a
: physical object (and that someone unfamiliar with Cortana would likely
: assume it as such). In particular it's very sharply defined, and reflects
: lighting just as you'd expect. Of course, one could always posit that it's
: some kind of super hi-tech hologram which can be like that. But you take
: my point I hope.

: Actually there are also some lighting related effects going on with her head.
: There's some reflection off the hair, and also the hair casts a shadow on
: the face. So even if my notion about just her head being holographic were
: right, that would be some pretty nifty holo-tech!

: Well, it certainly wouldn't be surprising that the styling of the conjectured
: physical body would be reminscent of her past appearances.

: Also seems a fairly natural thing to do, if the technology is available.

...well your theory certainly has piqued my intrigue. Her appearance is definitely much more physical in effect; I'm not sure about robot body, but the 'suit' certainly gives the impression of physicality - casting shadows, being lit from the front. Even the data bit represetations that used to flow over her body now seem much more like physically contained wires or channels on the surface of the suit. She's even adopted the forerunner glyph for the Mantle of Responsibility (though horizontally flipped) as a large raised button on her chest.
Anyhow, I do believe there was mention near the beginning of finding a way to becoming physical, so it would not surprise me that after the Domain she had to do so, in some manner to create a body within which she can travel. Seems to be the next expected step.