How in the hell did you manage that one???
My guess would be he hit her a little low and the blade got just under her skin and acted as a zipper, slicing her open from the inside out. I would also say you hit her on her left side, and she was closer than 20-yards. That's why the cut is so far down her right leg; it was a steeper angle.
Did you hit her heart? I would guess maybe you didn't, which is why she went so far.