Question: Spoilers. The end of the movie shows Meg at home, apparently surviving the ordeal. In the final frames, though, we see the eviscerated body of Meg wearing the same clothes she wore in the final fight. How did Meg get zombified? Every other zombie monster had to go through the breach machine to transform, but Meg was still human at the time the machine was destroyed.
Answer: Sorry, no answer here, but at the end I was left with the same questions. I gave this a watch because the music was supposed to be directed by a member of the Canadian band RUSH. I'm not a fan of zombie flicks, so I don't know the rules or conventions, but I do remember a long and tedious scene toward the end where the demented scientist was explaining to the sheriff how the breach device works and what he was trying to do.
Answer: I don't think this is a "zombie" movie - it follows different rules. The scientist and the machine were destroyed, but there were several altered human test subjects still alive at the end. The scientist's rambling explanation was that he wanted to instill the ability for humans to change their physical form. The best I can figure is that Meg survived the fight but one of the altered human test subjects bit her, transformed into an imitation Meg, and later followed her home to kill her. I suppose the "shocker" in the last scene was that the pregnant Meg was an imitation and would now start a new colony of altered humans.