This line is followed by a simile in To Kill A Mockingbird. If we consider the context of this situation it is most definitely part of a simile, however Scout is figuratively waving her words away, rather than literally waving away flies or something of that sort. The specific question being asked here is regarding a portion of a larger literary device (a simile). These particular words "waving my words away," can simply be interpreted as figurative language being used by Scout which is further modified by the rest of the simile that follows. Additionally, one can refer to these words as imagery since it is evoking the sense of sight. Normally, we see something being waved away or saying goodbye to something, which is what Scout is figuratively doing to her words. She is waving them off or watching them depart.
