and welcome to the forum!
I'm really in a rush, but wanted to drop a quick note off to you. I'll come back later and add more.
1. Metacam and Convenia should not be used simultaneously......here's a link to another case where you'll find links to contraindication warnings from other countries to this effect http://www.thecatsite.com/t/258906/w...ng-with-my-cat
The info from drugs.com
applicable to Canadian regulations does not speak to this issue for reasons unknown - I wasted half an hour looking for this info on Health Canada's Vet Drug site without success - that "crowd" has created a Vet drug site which is about as transparent as a black hole!
2. Why, on earth, your cat has been given 3 different antibiotics for a UTI is beyond my understanding........did they not do a culture to determine which bacteria was present?
3. I don't have time to calculate - you can do this - the maximum Baytril dose for any cat is 5mg per 2.2 pounds of body weight....my quick math says she should be getting a max of 18mg per day.....so, I think 25mg is about 30% - 1/3 too much. We had a resident Vet here, Dr. Lee, whom I remember being very directive on this point, to the extent of recommending that another member break up the Baytril tabs to get as close to that dosage as possible. You could do an advanced search here for "baytril" by username "Dr. Lee" and probably find his reference. I would reduce the dosage if it were me. Pill cutters are great for breaking tablets.
I'd recommend that you get as much water into her as you can - starting as soon as you can. Perhaps pick up some Fancy Feast pate style cans - "Classic" (not fish, though) and add a little water - see if she'll take those. FF is generally well accepted.
I would be extremely angry as well.