Hello, and welcome.
I'm sorry Jingles has gone through so much. I can feel your frustration and understand completely.
I think at this point, your best next step is to have her seen by another local, well-recommended vet (feline-only), if possible, and get a second opinion. She may need another round of a different antibiotic, but the fact that her urine was very dark yellow/orange, her liver may have developed hepatic lipidosis, which is caused by not eating and the best treatment is to get her eating again, which seems to be very difficult. She should be on I.V. nutrition, in addition to fluids.
It might be advisable to bring her to an ER vet center, where the specialists have more experience in diagnosing and treating 'mystery' illnesses that your regular has missed.
If her liver is affected, some supplements like Denosyl or Denamarin may help.
Holistically, milk thistle is also good for treatment of liver issues. However, first, you need a definite diagnosis, so please try to have her seen by another vet or an ER vet/specialist asap so she can begin on the road to wellness......
I hope all will be well with Jingles!
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