I think it is pretty standard for a vet to want to do a fecal on a first appt with that vet, especially since it would be considered a vetting appt. But I laugh when they ask for someone to stop their cat from peeing ahead of the visit. Worst case scenario, a cat wants to pee and can't find their litter box, they might just pee wherever they are anyway - be that on carpeting or anywhere.
If that whole endeavor does not work, and/or they don't find enough urine in her bladder during the appt, ask them if you can bring her in at another time for a vet tech to draw urine, sometime when you know she hasn't peed in a while.
My cat is a lot older than yours, but for the past several times she has had an appt. she has inevitably peed sometime in the previous hour before the time of the appt! Because of her age, I would never withhold her litter box from her, and I am glad that I didn't because I am not sure where she might have gone if she cannot hold herself from going!
If that whole endeavor does not work, and/or they don't find enough urine in her bladder during the appt, ask them if you can bring her in at another time for a vet tech to draw urine, sometime when you know she hasn't peed in a while.
My cat is a lot older than yours, but for the past several times she has had an appt. she has inevitably peed sometime in the previous hour before the time of the appt! Because of her age, I would never withhold her litter box from her, and I am glad that I didn't because I am not sure where she might have gone if she cannot hold herself from going!