Well her blood work is ok. Metronidazole
is usually prescribed for
parasites, but I guess general diarrhea would also warrant this. So if you say she is also clear of parasites, it could be the meds. They are pretty harsh, and can
rip up a cat
's digestive tract, just like in humans.
I would talk this over with your Vet and see if there isn't something else he could give , but I do think she needs to come off the present antibiotics, they are just a contributing factor to her diarrhea now.