It's not an intimidation response or behavior, as chickens don't do that to threaten one another or in response to being threatened, at least I have never heard of it.
But I do recall one case of an animal that did a beak clattering thing, and in this case it was in response to maggots eating the animal alive. These were not the normal harmless blowfly maggots which almost always stick to rotted flesh, these were two different species of very physically different maggots, segmented and hairy, that got into an apparently healthy bird through no discernible wounds, and ate him alive. It was too late by the time I discovered what was wrong, they'd eaten through the tendons and muscles all around his tail and legs, crippling him, and were into his guts. Very strange that none of my hundreds of other birds ever experienced those flies.
Since she was attacked by a dog recently I really recommend you check her wounds carefully. The beak clattering thing is akin to their preening motions when removing lice or external parasites, but of course they can't do that with internal parasites, so they respond to the itching the same way but don't move their beaks to the source most times.
Hope she has a better ending than my rooster did. Best wishes.
