Wait...so at the end? (spoilers)

I just want to know what the girlfriend was talking about at the end when she said, "You" or "he could've stabbed anyone."

Honestly I think people are reading way too much into this. George was fixated on Harry as he was the one prisoner who scared the crap out of him and just rubbed him the wrong way. That's why he was fixated on blaming him when he (George) started to crack under the pressure of the situation. Beyond getting people to stop taking their meds (which he probably did just because he was BLEEPED in the head given my experience with mentally ill people) George did nothing. The one cook who said, to paraphrase, "they're criminally insane. They don't need a reason". Has the reason for the riots. Criminally insane people off their meds during a blackout doing criminally insane things. George cracked during the situation (sleep deprivation, stress, seeing his friends killed). At the end when he yells "They got inside" he's referring to his own mind (where he is lost at the time) after he's had his breakdown. Enjoyable film with good suspense.

A few comments already posted are pretty spot on...

1) It was made very clear by the reflection scene that Harry Green is a personality disorder inside George Marshall.

2) That George must've crashed the van and killed his bandmates, explaining the girlfriends comments at the end about not his fault, an accident. Movie makes mention of how tired George is. And the whole asylum riot hallucination begins when George falls asleep in the pantry. It's pointed then that George was driving the van, dead tired, fell asleep at the wheel, and killed his bandmates, and he's been racking his brain with guilt ever aince, why he's in an asylum.

3) Fingers as a symbolism running thru the film.