How long has she been doing this? Is she otherwise active? I had a hen do almost the exact same thing the other day, she had a piece of hay stuck in her throat. She finally was able to cough it up and she was completely fine.
It could also be a respiratory thing but if it is she'd likely be acting unwell, not eating or drinking much, standing around. If it is a respiratory disease the other chickens are already exposed so quarantine at this point would be useless. However if she is sick she will need to be brought in, kept warm and given antibiotics. I would suggest Tylan 50. You can give a 1/2 cc orally for 5 days.
It could also be a respiratory thing but if it is she'd likely be acting unwell, not eating or drinking much, standing around. If it is a respiratory disease the other chickens are already exposed so quarantine at this point would be useless. However if she is sick she will need to be brought in, kept warm and given antibiotics. I would suggest Tylan 50. You can give a 1/2 cc orally for 5 days.