Lupin or Oddball need to take a look at this imo. It looks like my leopards tail.. but he got chewed up by my filter impeller. Personally I'de treat it with a low dose of melafix. Some of the other marks look alot like what I see with my fires after a tussle with eachother. I'm guessing some aggression with a tank-mate? heater burn gone un-noticed? also is this picture with or without feeding? if not after a feeding. I am strongly suspecting internal parasites.
So sorry to hear. She was a beautiful fish. She was one of the pictures that got me convinced to get my fire eels. Did you figure out what happened?