Tough decision indeed :-(
Only you can make that decision as it will be you that will live with the results of that decision (I hope I am putting this in a nice way)
At times like this it is hard to get traction in our minds as to the best course of action because the decisions at hand have consequences and they are not black and white
What if, what if, what if are the most traumatic questions to ever plague our minds and there is no perfect answer
This is not meant to sound cruel or harsh or unsympathetic, but when I am caught in an emotional circumstance that I cannot get clarity on, I resort to logic and then I add my emotions back into the picture again (no, I'm not a psychopath but sometimes it's the only way I can move forward on heart wrenching decisions)
Whilst it may be hard, I try and step outside of the situation and list the logical aspects of the situation, ranking them from highest priority to lowest (ie. What is the likelihood of recovery, what will be the quality of life afterwards etc), then after I have looked at things in this light I let my heart back into the picture because we are not black and white creatures and our feelings and compassion can achieve great things but they can be very misleading and distort a situation leaving us venerable to the circumstance
Sometimes I imagine the circumstance is happening to someone else and I am looking into it from afar to help me get things in context
Others here have given some sound advise, at the end of the day the final decision must rest with yourself and as always, the health and well-being of others should factor into the equation and what will be their quality of life afterwards
Your bun may be only 1 year old but she has had 1 year of a good life, some bunnies do not even get that. My kids first bunny and first pet ever was mercilessly killed by some evil person coming onto my property and ending his existence after only a few months. My kid and I were devastated. All we could gather that was positive from the experience was to acknowledge that little pixie had a great few months, being loved and cared for. Sounds like your bun has had a very cared for existence for a year, what a lucky bunny
I went through months of being very angry at whom-ever killed our bunny and felt so guilty that I had let him down as his career. Thoughts like "Why didn't I put that lock on the cage", "Why didn't I check that noise I heard outside on the night he was killed", "Why didn't I..."...In the end I had to realise that life unfolds as it unfolds sometimes and that circumstances are often outside our control and that we do not have full knowledge of everything that is coming and know what will happen from the decisions we make, all we can do is try and make the best decisions we can in the moment we are given to make them
I can't say whether or not to keep fighting for your buns life as this is your decision alone but sometimes in life a hand is delt to us that we ultimately have no control over and that all we can do is to make the decisions we make with the information we have on hand - sometimes the odds are just outside what we have the ability to change
All the best...