Oswald in the doorway: the blog of the Oswald Innocence Campaign, by Ralph Cinque

Mary Moorman certainly did not take her picture at an angle. 

She has never said she did, and she has never demonstrated that she did. And she was young enough at the time that her proprioception had no difficulty finding level. 

Whatever deviation from level that exists in the Moorman photo is due to the fact that it is a cookie-cutout of a larger image taken by Babushka Lady. There is more breadth to a diagonal photo (more area covered) and they had to reduce it when they converted Babushka's image to a Polaroid in replacement of Mary's.

Mary Moorman did not take a tilted image. She has never said she did. She has never demonstrated that she did. And, there is no reason to question her ability to hold her camera level. We can see her doing it.