It's tricky because we don't know at all how bodies work in this series so whether or not she has some substance and where it came from is difficult to say. I agree she doesn't have anything at all from Sora because she didn't have to return anything to him. I didn't think about that but makes sense. And it's funny you said that in every sense Naminé is Kairi because that is true and false at the same time. Actually in every sense she's NOT Kairi despite coming from her... which in turn makes her Kairi. Her very existence is so weird. A freak accident indeed.Keep in mind this is one of many hypotheses that runs in the Ansem Reports concerning Naminè. Which means they are not actual facts, just theories. Following them, Ansem never says she has Sora's body and soul, just that she was made/born from them, which is technically true. Kairi's heart left Sora. But he's nothing but an intermediary. Ansem also talks about how Naminè is the Kairi that came into contact with Sora's heart.
So there was no configuration -- all Sora did was allow Naminè to make her form corporeal (i.e. it's her own, not anyone's), not that she has any of Sora's discarded body and/or soul. Hence, a Kairi ghost/shadow made solid. Labeling her as a Nobody is even just a tentative term because Ansem has no idea what the heck she really is. Nomura once stated in an interview she may be a subspecies of a Nobody. Whatever normally applies to Nobodies wouldn't exactly apply to her. Furthermore, Sora did not need her to be complete (like Roxas and Xion) and there was no adverse reaction to her touching him in CoM in comparison to her touching Kairi in KHII when they were running together. Naminè started visibly dissipating into her.
Naminè's not a Sora, not even partially, and doesn't obtain anything from him. She would have had to be divided in two otherwise. That didn't happen at all as well.
The Sora aspect is taken literally when it shouldn't be the case. In every sense, Naminè is Kairi.
And basically a freak accident.