In the picture you posted, Obby, I can see a small, dark scratch closer to GBC's mouth. In my opinion, that's where Allison's thumbnail gripped onto his face, while the other fingernails created the longer, larger scratches.
Has it been confirmed if Allison was left or right handed? The scratches on GBC's face were on his right cheek, weren't they? If so, it would have been Allison's left hand that inflicted that scratches. I'm thinking that this would have been likely, if Allison was right handed, because GBC would have possibly used his weight to restrain her dominant right hand.
MOO.
I dont think we can conclude that it was her left hand unless we know the position she was struggling from.
If she had her back to his front and he was suffocating/strangling her from behind, it would be her right hand that tore his face.
(unless that little mark near his mouth is from the thumb. I'm not feeling confident with that. That could?? be one of the other scratches that were typical of shaving type scratches, but then again, you could be right.) MOO