Would you be willing to try some natural remedy methods before culling her? I saved a fish from an awful fungal infection years ago by quarantining him and then picking him up and using coconut oil with a drop of oil of oregano on his wounds. I literally spread it on the fish then put him back in the water. He was a cichlid and he had been fighting this for a long time and was surely going to die so I just figured I'd try to use some of my essential oils. If you mix a strong oil (like oregano) with a safe base oil/carrier oil (like organic coconut) they do not burn your skin, so I figured it may cause less harm to the fish (gills and skin which was exposed).
Fungus is all over the place, and it's crazy that infections occur when fungus happens to get into a cut or even a tiny scrape. I've read fungus can affect fish when they stress and lose their slimy film. That fish I saved is still alive today with crazy scarring from where his injuries had progress into the muscle, but he healed and is living the good life at a local fish store in their main display tank. I have heard colloidal silver can be used with fish, it may be worth a try before culling her. Also, tea tree oil has been used by some aquarists and that what melafix contains.
I am not sure with shrimp if the oil directly in the water would be best, but seeing how she is in a tupperware I'd use @ 15-20 drops of carrier oil (like coconut) to 1-2 drops of treatment oil, mix and dip q-tip, net the shrimp and swab gently in the direction that the swimmerets naturally fold, then put her back in her tupperware. Maybe the colloidal silver method would be easier to simply add to the water in the small container she's in... you'd have to google how people treat with that. It is sold at most vitamin/supplement stores. Anyhow, I know it was not the norm to do what I did with that fish, but meds were not working and I hated to see him suffer. I hope some of this info gives you ideas to research or look into further.