Strange behavior question.

Hello fellow chicken keepers.

I have a strange dilemma and I can't seem to figure this out.

Background information:
I have four hens who are 1 year old- all different breads.
My black star hen managed to get coccidiosis. I didn't have a vet confirm this- no vet in the area. I did lots of reading and the symptoms matched. We treated this chicken and the rest of the flock with corid for five days.
My well, three hens are doing great. They act as normal.
My black star chicken is slow. I never see her eat much, but she is still alive, so I think we are just being selective. We have tried hand feeding her, but she only takes a few bites.


Behavior problem:
She is attacking each chicken every time they come near her. If the other hens are within several feet, she will chase after them and attack. Otherwise, she is just still as stone. She guards the food and water and the other hens are afraid to approach.

We also noticed today her comb is getting white spots on it along her beak line and on the red area below her ears.
What could this be and what can we do about her behavior?