I'm not sure if it seems the case to anyone else, but when I saw this screen capture (left, or top) from the season three 'zombie' episode, and compared it with a shot (right) from the first season, from the Amy witch episode, it struck me that the first season photo makes the actress appear older. That may quite literally be the intention, to help compensate for the actress, herself, getting older. I don't know.

And it doesn't mean anything, really. I just thought it interesting. The Amy witch shot was rather retouched, maybe over-retouched (to try and lose some of the graininess). Perhaps too many lines were added or lost that it has aged the result. And what with different hair styles, and emotions being conveyed by the actress. Still . . .

And, too, I would say that I find the Amy witch 'candid' shot still the more striking, even so. It's the eyes, square at the corners, not rounded in disbelief as on the left, giving her an air of confidence it seems; which is hardly the emotion being portrayed on the left. And it's an interesting expression because as she has fallen into gently chiding her mother, showing something of an expression of defiance, it dawns on the character, and the actress portrays it as such, that maybe it wasn't so gentle after all, and that perhaps the look of confident defiance and sarcasm is misplaced; either that on she senses them about to enter into a serious disagreement. It's sort of right at that transition.

Interesting comparison of SMG (right) with Jennifer Aniston:
 
       
 
(from a dual fan web site (now gone) )