My gut feeling is that Kiri
is a form of Grace. I think that when Eywa attempted to bring her spirit from her human body to her avatar, she was too weak to do so (as Mo'at felt might be the case), but that it was possible to do so as an egg, and thus create Kiri not so much as a resurrection, but a true and literal
rebirth of Grace, formed with the collective power of Eywa directly, giving her a truly unique and personal connection to Eywa's consciousness.
I think Kiri initially is not aware of who she really is, but comes to discover this over this course of TWOW, fuly realising both the identity of her spirit and the meaning and reason of her link to Eywa when she attempts to connect to the spirit tree of the Metkayina.
I think that having Sigourney Weaver play her is a way to express this, and Weavers varying voice as Kiri throughout the movie leads us along Kiri's own journey of discovery or awareness of her nature - especially after she connects to the tree, from which point on she sounds (and acts) *much* more like Grace.
Does this make her a demi-god? I would argue no. Eywa is not a singular divine being - neither to human eyes who see a mindless, automatic system, nor to the Na'vi, who realise she is the collective spirit, memory and knowing of all life that exists on Pandora now and that has ever existed before. Immensely powerful, knowing and protective of life - Eywa is nonetheless definitively and absolutely a part of that life, and in no way separate to it in the way Abrahamic humans would conceive of a divine being as a creator who is separate to and divorced from the beings it creates and destroys, and who sits above as a stern dominator. As a result, Kiri herself is likewise absolutely a part of Pandoran life, and while "different" is absolutely not separate from it.
I will never be anything other than 100% a devoted fan of Neytiri - but I do love Kiri and I can't wait to see more of her
