I would be interested in reading the documented evidence should you have a link to hand.@Shadrach,
I understand your point about the severity of pecking. Here, though, it was definitely aggression (? the reason for it), and while Dotty clearly wasn't hurt, there has been documented evidence of increasing likelihood of egg issues if a hen is not allowed to lay for an extended period of time when they need/want to lay. Additionally, the stress this situation incurs on Dotty, if it continues over a number of days, can also cause issues. Given all of the health issues @RoyalChick has endured with her hens, she has every right to be concerned and to want to minimize the conflict, whatever the cause. I can't speak for @RoyalChick in terms of how she perceived the pecking in terms of severity (i.e. hardness of peck), but she did say that Dotty wasn't bloody. Again, imo, the real issue(s) regarding the behavior, is 2 fold: Dotty not able to lay when she needs to, and the amount of sustained stress she endures. Both of these can negatively impact her health in a variety of ways, the least of which would be to weaken her immune system...that alone is enough to worry about given the stress of sudden cold weather after a very mild fall.
@RoyalChick has quite the sizeable coop/run for the few chickens she has....so maybe just adding some hiding spaces/visual occlusion may alleviate this.
And, yes, I understand that a wild flock would occupy a couple of acres...but that is all about resources and resource protection. Here they have plenty of resources to go around and they have been a 'flock' for an extended period of time. So, why the sudden dominance/pecking order issues and why to this degree. (The pecks & grabs were quite strong! If you notice, one of the 'grabs' was strong enough to almost pull Dotty off her feet.)
I am not discounting that if a hen doesn't lay an egg for a particular length of time it may cause some discomfort, but long term health damage...
I would want to know how long. Hens have laid two eggs in quick succesion, mainly due to the first egg getting stuck and the other being delivered right behind it. It is far from ideal but with the hens I've known to have this happen there have been no long term ill effects that I've been able to see.
The issue is that one hen is preventing another from laying, if that is what Dotty intended when she entered the nest box. Dotty could have gone elsewhere to lay the egg. I have seen hundreds of such egg laying disputes if that is what that was. The tribes used to form queues for a particular nest box and in many cases get in the nest box a fight over who can lay. I've had hens get evicted from a nest box, go and call their rooster for support and end up with the rooster and both hens in the nest box scrpping over who covers annd eggs that are already there and how much room each is allowed to lay an egg.
This to me is normal chicken behaviour.
As for the aggression, we don't really know what the problem is and one would have to spend some time observing the behhaviour between the two in other situations to make any reasonable assessment.