It hit a varicose vein, and per the article I read, cause of death was blood loss. Most people don’t have varicose veins on their upper bodies, so I think it’s more likely a leg. The article also says she was elderly and the puncture “bled profusely”, hence the speculation about blood thinners and cognitive issues. Direct pressure on a varicose will stop bleeding, but if you’re not “all there” you might not remember to do that.
My idea was tha knocking her to the ground rendered her immobile thus leaving her more vulnerable to the attack on her legs.
Even an attack that started on the legs could knock down a person unsteady on their feet however.
But an elderly lady knocked down would likely have a hard time getting up again and may not have the muscle tone necessary to reach a leg wound from a prone position.
If she could not sit up she would have difficulty defending her self from attack on her legs by the rooster.
Lack of strength is all that is necessary to make this attack likely fatal. I don’t see cognitive impairment as being relevant. It could be involved but I don’t see it as necessary to the equation.
It’s nature for chickens and a lot of other birds to ‘peck’ - (I don’t know about chickens - they may come into the world pecking - but when you hand-raise a lot of wild birds, they have to learn pecking from you, as they would from Mother Bird.)
Birds peck at things that they think might be food.