I'm so sorry. It is very hard. Our pets are so much more than just "our pets". I've lost 6 rats now, and soon I will lose my last, 7th, and be ratless for a while. It's just as painful everytime I'm afraid, because they are all so unique and individual. After a few years, however, you remember so many good things about them, that the sadness and pain of losing one is overshadowed.
I hope your vet agrees to give you the medicine. If not, I would advise pts as she is not eating or drinking and that is a bad death. Don't lose hope yet however. Please, make another thread about her PT. I think no one is reading this thread, because they have already welcomed you to the forum and don't think there is anything crucial going on!!!
THe other members can help you our greatly, and maybe give you more resources to convince your veterinarian.