I would guess that her aggressiveness is from being neglected as far as feeding and handling. I recently aquired a boa from someone in the same condition, only I didn't give them any money for it... He is pretty aggressive and we've gotten into it a couple of times. Yesterday was the first time I picked him up without him threatening me with an open mouth. I was getting him out to give him a larger water bowl, and since he was all right about it, I kept him out for a few extra minutes.