This is such a very sad situation that you find yourself in. If she has been sick since you have had her, did the vet mention anything about possible Feline Infections Peritonitis? FIP? Even, if that is not the underlying cause, it sounds like your poor kitten has not had a very good quality of life since she has been born.
Your vet, if you trust his experience, may not be trying to make you feel badly when he talks about euthanizing your kitty. If you really can afford to, and you feel he is not giving your kitten the best treatment, then perhaps you can try to get a second opinion from another vet. But, it sounds like your kitten is in pain, and each time you have to take her to the vet's she is getting stressed out, which is not good for her, or for you.
Sometimes, if we really love our animals, we have to give them the kindest gift of all, no matter what their age, and that might be to euthanize her, if nothing can help her condition improve.
Some people might recommend to just stop the antibiotics, and see if she could perhaps be having allergic reactions to the medicines she is on. What antibiotics is she on?
Before giving up all hope, I think I would try to get her on a good canned food, at least temporarily, such as Hill's Prescription A/D, to build up her levels of immunity, keep her away from any other animals you may have, use a warm mist vaporizer to help her breathe easier and make sure you are keeping her indoors only, and if you believe in God and prayer, keep praying for your kitten.
Has the vet done x-rays on her, to see if she has any fluid around her pleural area of her chest? Sometimes, FIP, can be a nasty disease that is hard to diagnose, but if this is what your kitten possibly could have, it most always is fatal. Has she also been tested for Feline Leukemia, or Feline Immunodeficiency Virus? I have an FIV+ cat, and he has been with us for over ten years now, but he came to us, very young, and very ill.
I have a kitten also, that my vet thought may possibly have FIP and she did an x-ray and his chest was normal, although he sounded just awful! We had him on antibiotics for weeks, and he finally cleared up. Then found out, even with the worm treatment he had gotten before I had him, he tested positive for "roundworms" last year. So, we had to treat all of my cats.
So far, he has gained a good bit of weight, and if your cat is still strong, as you said it takes two experienced people to do her fluids, then she may still pull through this. But, please don't let her suffer, is there is no hope.
God bless and good luck and I will keep you and your kitty in my prayers!