Am so glad she was better at the second vet, and that he was more positive. I have had a couple of cats with liver probs, thinking about it, Snowy did drink more than Ginger, but none of the vets we saw (vet had a lot of locums at the time, so it was a different one each time!!) said it was a side effect of it - but reading about liver issues now, I think most of those vets dismissed a lot of things.
It is a shame you hadn't mentioned insurance before, I have insured 5 cats aged 10-14.5 with Sainsbury's, they have accepted them all, and I now get them insured before their first blood tests, just in case.
Good luck with the results.