The only other question I would add at this point is have you checked her for mites & lice?Good morning and Welcome to Backyard chickens. Just wish it was under better circumstances for you.
I have a few questions to try to better assess the situation.
What breed is Ginger?
How old is she?
What type of antibiotic is she on?
Is she eating and drinking good?
Is her poop normal?
If you took her to the vet, what did the vet diagnose her with?
I would error on the side of caution until you have this figured out. It absolutely could be contagious and could weaken or wipe out your flock.