Okay so, new theory courtesy of my sis, sitting here brainstorming. What if Madotsuki's parents were archaeologists/anthropologists in South America. It's crazy down there with all kinds of wars and stuff and they could have easily gotten killed on the field or worse. Maybe she's still in a building in South America and doesn't want to go out because she might get attacked, kidnapped, etcetera? This takes both the Aztec/Mayan aspects and the isolation theories I've seen before and mooshes them together.
Some of her dreamworlds might map to "Xibalba", the Mayan underworld and its different "houses".
http://river-styx.net/aztec-myth-mictlan.htm
"Mictlan is the lowest layer of the underworld, situated in the north. Every soul, except those of fallen warriors and women who died giving birth, have to descend to the underworld. Here, their souls will find eternal rest. However, they first have to make the dangerous journey to Mictlan. At the burial, the deceased are given magical powers and with the help of the god Xolotl, they are able to make this journey safely."
Effects? The journey THROUGH Madotsuki's own personal Mictlan?
"There are records of finding burials in various postures, most common of which, was the fetal position - a return to the womb. Interestingly, it was not the life of an individual that determined his final resting place but his death. "How" one died was more important than the life itself."
The girl in the igloo and the girl in the closet and Madotsuki's own sitting position reflect this exactly... so do a lot of the things people seem to pick up from "monsters representing pregnancy"
http://river-styx.net/maya-death-xibalba.htm
"So, what do we know? The most important gods were the Sun God, the Rain God, the Wind God, the Maize God, the Death God, and the Suicide Goddess. There were human sacrifices, and the custom of "bloodletting" was a common practice, the tongue or genitals being the usual area."
So could these Gods map to some effects?
"The Maya did not regard life or death in the same way as we do today - the fact that they had a Suicide Goddess makes that clear. She is Ixtab, and is depicted with a rope around her neck. Since the Mayans believed that "heaven" lay beyond a suicide, it is believed that this practice may have been quite common. Death was closely intertwined with life, for they believed one was first dead, before one was born, i.e. had life. Death was a doorway to Life, and Life was a doorway to Death, thus death and death rituals were quite important in this society."
This just kinda maps directly to the end.
There are a whole lot more but basically, if someone writes a "Journey Through Mictlan/Xibalba" YN fic I will love them forever. That or I'll just eventually write it myself.