Okay, so for a long while now, I've theorized that the difference between psi powers comes from where different psionic characters access other people's brains. I'm not saying they can't access other parts of the brain, just how they get in and how their powers first manifest. I've been reading The Future of the Mind by theoretical physicist Michio Kaku, and part of the book kind of backs me up. (Not that I believe any of these powers are possible.
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One chapter is dedicated to the evolution of the brain from reptiles to mammals to humans, and is pretty interesting how it matches different power sets.
The "reptile" brain, containing the brainstem and cerebellum, controls instinct, instinctive functions (like breathing) and movement. That could be how Karma gets in.
The much more recent "human" part of the brain, the neocortex, is the area controlling cognitive function ("I think, therefore, I am" and 1+1=2). That's the part telepaths usually seem to contact first.
In between, we've got the "mammalian" brain, aka the limbic system. This part covers sensory imput, emotions and memories as well as desires -- hunger, pleasure, etc. That pretty much sums up what Dani draws on to create her illusions.
Of course, this doesn't cover her "solid" illusions (or the telekinesis that some psionics have), that would seem to bee more along the lines of manipulating quantum mechanics, which is interesting given her power switch back in the '90s.