Well, not sure about worse scenario? I suppose that would be she declines to the point you need to put her down.2 roosters, have not noticed any type of feather loss or signs of bullying. I'm always trying to observe the girls and look over them frequently.
We wont put her back in with the flock until we see improvement, we do not want her to get hurt. What would be the worse scenario?
Depending on what ails her, even if it's Marek's, she may "recover" after a period of time with supportive care.