Okay, wild mass guessing time. Ever since the "Erin is hallucinating" arc started, there's been a niggling feeling in the back of my head that maybe, just maybe, the hallucinations aren't hallucinations, but some kind of aliens escaping through a rift in her brain. I mean, the name of the initial story arc was "Stowaways." That sounds less like she's imagining things and more like she's got something real taking a ride around in her brain. Plus there's <link=http://www.escapistmagazine.com/articles/view/comics/critical-miss/9010-Stowaways-Smash>this comic. I know it's a reference to a painting by an artist that Grey Carter is a fan of, but I wonder if there isn't a secondary meaning there?
Or the comic could just be about a woman slowly slipping into madness and depression. That's always a possibility.