If anything, "she's got steam shooting out her nostrils", as she snaps her beak at the cats fur, tearing out clumps. If they even remotely try to stand their ground, much less fight back, she KICKBOXES, like a Rooster would! (Video of a Rooster jumping and kicking a womans shoes, shes not h
urt, laughing throughout it while yelling a little from surprise)
Here we see Whole Hen has cornered Jasper the cat behind a chair inside our house, as he looked at the Hens, Whole Hen ran through the cat flap inside and pushed him back. He wasnt touched at all by her, just frightened off.
You can see she watches him continuously, his every small movement gets a reaction from her, until he leaps onto our washing machine, where hes (mostly) safe from her. Its easier for a cat to jump that high than for a Chicken to fly there, but she *could* follow him if she wanted.
The cats are safe, shes never hurt them as they've hurt and killed Hens, so I guess in a way its good that she looks after Yellow Hen. The only bruises are of the "alpha predator" cat egos being crushed by this protective bird.
Another of my Chicken Friends, Curious Hen is highest up the Hens social order, yet she never keeps cats back. Curious Hen happily sleeps on my lap, or even rests on my shoe! :-)