Medicate the whole tank.
Sadly there really was no way to get her to eat because she was too far gone... As you realized later :( Sorry you lost her. Was she a new add? Quarantine an and all new fish for at least 2 weeks, to ensure the safety of all the other fish. It also allows you to catch diseases early if you focus on the new fish by themselves.
Breed for the breed, not for the money; the words any REAL breeder would understand.
You must know nothing in order to know all, for all is nothing and nothing is for all.