She had cancer and had a tumor in her ear. She had surgery 3 times to remove the tumor, then a 4th time to remove her ear completely. She went through some intensive chemo twice. Then the tumor grew back again, about the size of a tennis ball, hanging off the side of her head, bleeding all the time etc... Our vet did EVERYTHING to not put the dog down, but it was a situation where the vet knew it had to be done. The vet said the dog probably wouldn't survive another surgery and even if we did it would just keep growing back. There really wasn't any other option.
People do ask me where we had it done but I won't recommend it because it isn't "A vet who puts dogs down". I think it was as hard for the vet as it was for us.