I am behind 40 pages, so please forgive me if events have foreclosed my reply here. But I am hoping I might be able to help you with your stress, by re-framing the situation a bit. I am relating to you through my own experiences, so forgive me if I've got a terribly wrong impression.
As I see it, the short summary is that you are stressed because you are feeling how "in the middle" everything is, and you don't want to dilly-dally on doing the best thing for Bella, and you don't want to jump the gun either. You see the potential bad outcome, yet still have hope given how she is, still interested and chatty. You are wanting a resolution one way or the other, and that can be stressful when that is not forthcoming, when you are getting very mixed signals. You are looking for progress and a future of certainty. Certainty is an illusion in the chicken world, besides in most of life. My advice is to let go of some control over the decision to euthanize or not, and trust yourself to see the answer clearly when it reveals itself to you, and what may be needed for that, as the vet said, is to allow some time. Give yourself time also. Slow down. Feeling very undecided all the time is incredibly stressful. So what can you do about that? Decide to not decide. Take a few slow deep breaths and merely "be" with Bella, how she is in the current moment, without thinking about what the next steps for her are. Not knowing what to do means you do not have an answer from her yet. That's okay.