Sorry to hear about your cat. Lethargy, loss of appetite, vomiting, wt loss etc come in later on. I would recommend booking an appointment and give lots of love that day, keep her happy. When you go for euthanasia appointment, get the payment part done first because you wouldn't want to stand around to wait for paying afterwards. I usually give them a sedative and painj inj. Then after 10-2 min once animald are calm and sedated, my techs bring them in the tech area to place an IV catheter which might be difficult to put in kidney cats. Then they would bring your pet back to the room and do the final inj through that catheter. It is instant and quick. Take your time at any step of the process. Everyone there would understand their situation. Take Care