Graham's Sister

In the Color Pages of Another Junk Railroad, Graham Specter mentions having a sister. The only thing known about her is that, out of anger, she once pushed Graham from a fourth-story window when they were children. In his ramblings, Graham does not mention what she looks like, her name, or even why she was angry enough to push him from the window. It is possible that she may be something he simply made up while trying to make a point, but that is unlikely a she was an unimportant detail to the story.