I have a horse that was a rescue from a horiffic situation. He came to me starving, 500lbs under weight, no muscle, no fat, infections in his feet, gums and various other issues. The vet said euthanize on first glance. Second vet said the same. The third said he will never fully recover, will always have issues, health issues and would not live a long life but if you want we can try. He was 12 years old at the time. Buck is now 19 and going strong. He is on meds and will always be difficult to feed, but he is a beautiful horse with a wonderful personality and I am happy I did not end his life early. My point is, that with proper care, Sadie could live a long full live despite what the vet predicts. You can choose to give her everything she needs to be happy.