I most sincerely respect and admire the facts that: You volunteer to work with shelter animals who, in general, have been badly mistreated by their cretin owners. You took into your home and heart an older dog who, in general, very few people will adopt and usually are the ones most in need of adoption. You dealt to the very best of your ability and to the very end with her medical problems and didn't just take the easy path and put her down. You gave her precious time to once again know love and caring. Lastly the fact that you had the morality and courage to be there with your dog as she was put down. So many just "drop them off".
We have four of our own dogs at present so pretty much impossible for me to take in another.
I most sincerely commend you for your actions. I'd say humanity but that's not much in the way of commendation