Just had another think about this and even more convinced that the smear is not mirrored. If it had been, then the circled area would have been far messier than it appears. So imo, definitely caused by a thumb, finger or something else being dragged across the wound once or twice from left to right, then lifted off to create those two dark blobs.
Well as I said according to Prof Knight there's a momentary delay in blood presenting. Assuming this was the case here, the rifle (with or without silencer) was already out of the way based on soc image. So much for 'drawback' &%+((£
Based on the pathological evidence SC was incapable of voluntary movement after the second immediately fatal gsw so would not have been capable of putting her hand up to the second wound. Maybe after the first gsw she put her finger(s)/hand to the wound and transferred it to the second wound to identify the site. This seems unlikely as I would expect to see a correpsonding smear elsewhere and I can't see one.
SC's found location doesn't look right to me. Why would her head fall to the left of the cabinet? Surely it would fall straight back and end up wedged between her neck and the cabinet? I think she was nearer the connecting door and moved by the raid team in their haste to check behind that door.
The bloodstaining to the left (as I look at the image) looks to me as though it has dried and then cracked as the skin has expanded due to swelling - there's visible bruising to my eye at least.