Hi Maggie,in my estimation that second shot was the " shock " one which followed quickly after the first which appeared as an unexpected aim after a short pull-back following that first shot,a jerked one best describes it,in my language anyway.
Not that of a professional obviously.
I know what you mean Lookout but imo it would have been a massive chance that it would shoot Sheila where it did, I would expect a reflex second shot to have missed her altogether, hit her in the chest or throat or even the face but that second shot was well placed under her chin in quite a difficult position to get at.
The first shot was at 45 degrees so how did the rifle get so quickly into the position to shoot her under the chin? I am sorry to say this but it doesn't make any sense otherwise imo.