Some more thoughts.
On the whole I'm more pleased with the shared-dream scenario than with what I had speculated was going on. I think.
I had imagined that Nioi might be piggy-backing a dead alternate-universe-female-Elliot's soul into Ellen's body and Ellen would learn that person's life through dreams. I presumed this person's death was tied to the evil alternate Tedd.
That would have been really bad news for Ellen.
Other speculations veered off of that road (e.g., not piggy-backing a dead fem-alt-Elliot's soul, but implanting her memories of years 1 to 18 -- or even a living fem-alt-Elliot's memories). I thought Nioi was one way or another implanting memories into Ellen.
This living-in-a-shared-dream thing is certainly different from that.
But I'm still worried as to who designed the background world and moves the dream-image residents.
I mean, how do you create a "Mr. & Mrs. Dunkel as if their only child was a girl living in a world half-populated with furries"? Is the technology identical in both worlds, or is there a mix of technologies in the dream world? Who writes the basic script?
In the real world, people make decisions sometimes randomly and sometimes very thoughtfully, and both have all sorts of consequences. Who supplies the fake "free will" to the characters surrounding Ellen and Kaoli? Who decides which persons will be good (and when) and which persons will be bad (and when)?
Was everything happy and cheery there in dream-land, or was there crime, disease, etc.? Who decided what situations Ellen and Kaoli had to face, and when?
Nioi claims this was to give the two of them 18 years of experiences. Well, who decides whether to give them happy experiences or sad experiences? And won't that make a huge difference in how Ellen and Kaoli come out of this psychologically?
Still a lot of unanswered questions.