apparently, Yukari doesn't canonically hangs out with
- Eirin
- the Watatsuki sisters
- Aya (the invincible, who can defeat even herself and onis -- and Yukari, as well -- without shooting, or some could say, without trying)
- Flandre
- Yuka
- Shinki (I did it for the lulz)
- Dragons
and apparently, Yukari doesn't canonically toy with many of the weaker characters, one of them being Chen. Even in the games, Yukari seems to make less fun of her opponents than other characters.
The outside world being Yukari's dream wouldn't explain how the lunarians threw the American flag back at the earth, said flag having ended up in Gensokyo (the three mischievous fairies find it); and Gensokyo being Maribel's invention (as in, Maribel sleeps and becomes the Yukari persona for half of a day, and vice-versa) could work, in a sense that, while the Hakurei border was meant to seal the youkai-populated region so that they wouldn't get out, the great boundary that keeps the illusional world and the real world separate served the purpose of attracting the youkai into Gensokyo, meaning that they were illusional beings from the start, and would otherwise progressively diminish and fade in the outside world. But... how would Maribel live for so long? Unless Yukari's past is a lie? (like, Maribel and Yukari, and both worlds all along, are actually Matrix slaves lol) Chances could be that even the youkai and the Hakurei border were purely fictional (conceived tales made out by scared or creative humans), not existing from the start, or the youkai's history doesn't acknowledge neither of the two barriers, or only the Hakurei barrier; either way, making things actually different from what Maribel thinks or dreams. That is, if they are really the same person, though no one can really guarantee that they are, due to lack of conclusive evidence.