These are not mutually exclusive traits. A human nice rooster will still protect his hens* and a mean one doesn't guarantee he'll guard them.
* roosters are generally not capable of defending against any larger predators and even then, it's a self sacrificing 'fight'. They're a distraction...
She won't develop immunity, if you use it once a month, the worms might but you're not doing that.
She "would be hunched over and lethargic with a pale comb and wattle. " those can be symptoms of not getting the nutrition shes eating. it won't hurt to worm.
Hmm, I don't know where the pigments come from. That's possible that she's anemic. I suggested calcium just in case she was struggling with a second egg.