She's not the only researcher who has argued this... But it's a contemporary concept that I intuitively disagree with. For one thing, it's not falsifiable--it's impossible to prove the nonexistence of a thing. And we can't take an instant poll of the recently deceased to ascertain where exactly they are at--even if their "at" bears any relationship to the physical universe. It sounds trivial, but it's not. The "where" of where we ultimately go is unknown, and unknowable, because--by most accounts-- the "afterworld" can't be physically mapped; there is no place that we can point to in the physical universe and say, "That's where the afterworld is." When survival personalities are asked--"Where are you?"--they're unable to say. The closest human analogy that I can think of is the dream universe. We've all visited vivid physical landscapes in dreams, but whenever we try to drag a part of this world into the physical as a token of our visit (I've tried), it vanishes when we wake up.
Even in the physical world, concepts of location and distance can only be approximately described, because every object exists only in relation to other objects--it does not absolutely exist at a set point in the universe. When you remove yourself from the three-dimensional consensus universe, with its relative reference points, you lose even that--you have *no* reference points.
Still, we instinctively try to frame the afterlife with physical reference points that hypothesize different "levels" that exist "closer" to the physical world, such as an "astral plane," or further away, where God "is." (And, for all I know, this may be the best approximation we can make.)
Despite all this--I still think that there's evidence for a "lower" astral level that--for lack of any other way to explain it--is not too "far" away, and that quite a few discarnate personalities linger there.
For one, there are simply too many accounts of a dark, vast "gray" level that the newly dead pass through on their way out of our physical system. The prolific OOBEr Robert Monroe talks about this level in some detail. Ancient historical accounts--probably derived from ancient OOBE and NDE stories--uniformly mention a purgatory-type level that traps the unwitting and unworthy. This level pops up in a number of contemporary NDE stories.
Secondarily, the whole cottage industry of "soul retrieval" and rescue--which some people claim to practice on a nightly basis--is predicated on the assumption that some souls can become "lost" immediately after death. Indeed, the Christian concepts of sin, salvation, and of becoming "saved" versus being "lost," may describe something that is literally true... When you "sin," you cut yourself off from God, and you might become "lost" after death in some lower astral level.
All this, of course, is a vast oversimplification and probable distortion of a process that we can't yet comprehend. Mankind has grappled with these concepts and codified them in religious beliefs through the millennia, without much success. It's not likely that we--using a metaphysical vocabulary that's hundreds of years old--will do much better.