I have a theory that Mado is at the home arrest after committing something against the law.
In that case it explains why Mado didn't "died differently, perhaps in a car chase or to drugs or STDs, etc".
Her being sociopath explains why she doesn't socially interact in a normal way with people in her dreams.
>Maybe her dreams would have been never about feeling down, so much as increasingly more boring physical activities and manipulations and brutalization of everyone around her.
But the residents of her dreams are formless brutal creatures. Maybe that's how she wants to see other people: damaged and deformed. You can't say for sure that Mado dreams about feeling down.
Also think about encounters with the game's human-like characters:
1. Shitai-san: dead
2. Monoko: deforms
3. Monoe: disappears
4. Poniko: becames distorted creature
5. even Masada-sensei: his "home" crashes
6. Toriningen: insane and deformed
So every human character is manipulated and brutalized in her dreams. And she doesn't seem to care. Not to mention severed heads in White Desert.
Also notice how every human character is distant. You have to travel in the game for a long time to find even one of those characters.
And none of them gives you the most important thing in the game: the effect except Shitai-san
. That means that Mado don't think humans are that inportant except they are dead
. Just think about it.