I think that the concept of retreating into a fantasy life is not ego-alien to most people at some point, as it imbues one with special abilities and allows a much more rigid control over what happens in our lives. I'm guessing this may echo more true in the case of people who, for whatever reason, have less sophisticated social skills and feel threatened by the sometimes daunting task of adapting to this nihilistic postpostmodern world. Now the concept of creating a crystallization of this fantasy life in everyday situations is somewhat plausible, albeit not so much unless we delve into the world of psychosis. Ben seems to first imagine his virtual girlfriend as personified after he takes the pill the bullies feed to him (I'm assuming it was some sort of amphetamine), shifting the paradigm along the lines of substance-induced psychotic disorder, with lingering effects up until the end of the film (even though his mother dismisses the potential severity of the psychic process brewing - after all, psychosis is neurotoxic, so to speak). She is much more concerned with the overarching social adaptation in a sadistic world than achieving any real resolution to underlying causal issues. Technically, the film was visually appealing, the insertion of video game images rendered more palpable the idea of associative thinking that goes on in everyone's minds, you don't have to be on the autistic spectrum to fit into that mold. I didn't love the actor's performance, the build-up was reasonably OK, I didn't expect the twist, and yet it wasn't terribly fulfilling nor incredibly realistic that he wouldn't be vilified horrifically (more so) after staging such a farce. Anyway, the bottom line is that the story, in the end, is one of hopelessness, seen as how he was able to "win" the battle against his persecutors, and yet his ego defenses were so clearly feeble, and the external environment so threatening, that his only choice was to spiral into a psychotic world, so comforting and maladaptive that there may be no way out.
