Why aren't you human?

Prolouge

as I watched the girl in a lily-colored dress smile at me through the lens I took the picture and then I looked at the photos in my hand, one, Two, three, one. I began looking at each photo carefully to see if I noticed anything that was slightly stranger than the others, or different. Each looked the same as one others. there was a girl in a white dress with long black hair, I stared at each photo individually hoping to notice something different from the others, something stranger. I looked at the girl in front of me and back at the photos
"I don't think you captured my beauty." She said in a serious tone that made a chill go straight down my back, I stared at her, then back at the photos. I noticed no difference whatsoever, she kept making the same comment "I don't even look human in this one!" She then snatched the third photo out of my hands, I couldn't tell what was different from the others though, she said her neck looked too long and her hair looked uneven so I had to retake the picture. I refused several times and told her to stop asking because the photo looks fine.
Instead of agreeing with me she grabbed the other two and walked off. I still couldn't tell what was wrong with this photo, it looked fine, what wasn't human about it? A few hours later I went to the bar and sat with one of my buddies and showed him the photo, he said she looked ugly and deformed. Like a parasite.