Can you take new pictures? It could be a type of fluke?
Try a broad spectrum parasite med like API's General Cure http://www.thatpetplace.com/pet/group/23771/product.web
Honestly, in this situation I would try Potassium Permanganate. It can only be purchased online and must be used carefully but it does a good job of getting rid of parasites and other infections that other medications can't. https://www.pondrx.com/products/16133.html
You can find smaller amounts for a few dollars on ebay. Definitely continue salt treatment.
It would also be best to get her back in a heated set up; cold water is going to stress her out and prevent recovery. How large is her normal tank?