I argue that Annie's surname cannot be "Mograph". In the Nexus article discussing the process of creating her origin video, they refer to the "mographs", the motion graphics of the animated login screens. There is a piece of evidence from the BTS video denoting a possible full name for annie, but we should keep in mind that they were creating the soundtrack for her origin video, not the character theme.
The development information mentions that the art style of the video was inspired by the mographs, even before Annie was chosen as the subject. From evaluating this disconnection, it is erroneous to establish her surname as a term that explicitly connects with this art project.