I'm sorry about your hen. If you can't get her to eat, she will likely pass. If I were you, I would start tube feeding. You can tube the medications/oil along with feed, and that will hopefully help her recover. @casportpony has experience with tube feeding, she may be able to help. She also has articles written about it which I will link below.She has been fighting the respiratory issue for about a week and a half. The issue is that her appetite seems decreased. She usually runs up to me everytime I go outside hoping for treats but now I have to go right up to her and even then, she will get close to it, maybe take a couple little nibbles, but seems generally uninterested. I’m not sure how to get her any medication when she won’t even eat much.
Thread 'Step-by-Step Tube Feeding Guide - Pictures - Under construction'
Even if you did quarantine, its so so hard to keep them separate enough to not transmit disease. The only way to reduce the risk caused by new birds, is to not get new birds. For most hobby chicken keepers, we decide to take the risk.