I think what the military and Holland were both implying is that neither side had ever managed to get into the Coralian. Since Adrock believed them to be sentient, then that probably means a great deal about Renton, since that would imply that Renton was accepted by that one into the dream world.

Also, if Eureka is one, that must mean that in some way at the least, Anemone is one. Maybe that has something to do with her psychosis and why they pump her full of rage medicine all the time. Was she torn from their world where Eureka was willingly given to this side? Or is she some synthetic military made one?

The thing I noticed early on was Eureka has a red circle (usually appearing as cresent moons, unless her eyes are fully open) in each of her eyes, whereas Anemone has a single red slash through each. I wonder if there is any signifigance to that difference. It makes them both similar and different for sure.