Im so sorry to hear about your dog! I had a cute golden retrevier that my parents bought for me when I was thirteen. She suddenly got very sick two years ago, and I was on my way home to San Francisco to pick her and bring her to davis (one of the best vet clinics in the nation) when she died.
I was very said, especially because I hadnt seen her in a whle. Keep in mind though if it is nothing the vets can fix, your dog will be happier when she doesnt have to deal with the pain. Not sure if that helps, but I will pray for her.