I am sorry to hear about your loss. Sometimes they come to us too far gone to be saved dispute our best efforts. You did absolutely everything you could, and please take comfort in knowing she passed feeling safe, warm, and loved. That is really all any of us can ask for when our time comes, whether human or feline. I hear what you are saying that, in the end, it was almost a relief to see her go and know she isn't suffering any longer. Sometimes, that is what is meant to happen and is the best thing that can happen. You gave her a peaceful crossing and that is by far the greatest gift you can give.