Her feeling sickly might well be the side effect of all the medication.
Instead of mixing doxycycline and metronidazole you might want to try sulfadimethoxine to get rid of the coccidia and it might even help with some of her other problems (enteric/soft tissue infections).
And try the Moro...
Have you tried the Moro carrot soup? It works wonders restoring the gut balance and even catches bacteria resistant to antibiotics.
https://www.backyardchickens.com/threads/ascites-not-eating-scaly-leg-mites.1441960/post-23973664
Other than that, you could still try the rather drastic method...
Well, then I would feed her lots of coconut oil, chilled to break it into little lumps easy to eat. And multi vitamins (Vitamin B complex+Vit. D3+K+E+A+ electrolytes.
Crop surgery is performed without any anaesthesia and for me, that would be the thing to have done in the first place. I hope she is still strong enough for it, but usually it does not take more than 10 minutes.
Your vet has to be careful not to injure the large blood vessel right across the...