As you can see in the image in the upper left corner, Zoey’s hands look indeed strange – not only that it seems she has three hands but, if she does, the number of fingers doesn’t seem to be 15! Which is even stranger, you know… like she’s twice a freak or something.
Of course, probably spending time in an infected world and having zombies all around you might have some effects on your body parts, but it’s still strange. Logical explanations aside, it’s most likely that Zoey’s three hands are actually a not so well done job by the artists. At least her face looks OK!