Ella clearly said that Amber wasnt tied to the 12 core trait (so apostles), the Qliphot is quite something else and we arent exactly sure by what Ella meant by it by special relationship with body and truth.
But now the way Amber power work is quite similar to Undines, liquid body and total control over it, their attacks also are limited by the amount of water of their body like Amber who have a limited amount of water too and can take control of other bodies of water and to make it her's, and of course the way Undine can infuse their water with other effect and the way Amber drain power through her water.
Finaly she somehow was able to be fused to her sister by Tanos without losing their individualities, leading to be as powerfull than if they had evolved already, kind of similar to the fusion of Undine.
We can clearly see that Liz inherited the full ability of Strenght eater, when for Amber, it's more close to Undine but with the draining ability used by strenght eater (who isnt the ability of strenght eater either but something else , it's quite curious .
Also, the way the black water tend to avoid Amber can make us think about how the undine fear to reunite with the rest of the black sea, which could give us some hint about what the great ocean realy is, because Amber clearly wasnt just infected by an Undine, otherwise she would still be tied to apostles.
But even that doesnt explain why it wouldnt be tied to the 12 core trait though .