Ghost Over the Shoulder

Mary sent us this picture for you to view:

"Hi...I was actually wondering if you could tell me if this picture really has a ghost in it or if it is just an optical illusion. I was taking pictures of my house for my dad to send to our family in NY (I am in Florida). Well, my mom hates pictures being taken of her...but she appears in one of them way off to the side (In the far left corner of the picture). I showed them the pictures when I was done, and said, "Ha, mom we finally have a picture of you...even though its small." I then zoomed way in on her to poke some more fun...and then i saw what appears to be a face over her left shoulder. I said, " do you see what I think I see?" We were both a little frightened, but a little curious to see if this indeed was what we thought it was...a ghost watching over my mother??"