With Kreia, I don't really think there will ever be an official confirmation of 'what' (or perhaps 'whom'?) she really is. There have been many theories, and I can clearly see where you got Arkanian.
From the speculation I have read, Kreia seems to be an Echani. There was a really good Let's Play walkthrough that really put together the evidence (link here
) and pieced together a lot of interesting tid-bits. But unless the new Revan novel has a grand revelation regarding her, I would imagine that it will always only be rumors, theories, and speculation.