Help for Sick Kitten

A sick kitten came up on our porch one night, cold and wet and near death. We took her in and took her to the vet, they gave her a round of antibiotics for an upper respiratory infection and told us to follow back up in a few weeks. After doing so, she received her first set of boosters and we were told to come back to get her second round of boosters if all is well. Since then, she has gotten worse. She's lost weight, she can hardly eat/drink, she has blood in her mucus, she's been letting off this foul odor and she occasionally messes (unsure if that's because she's sick). We just recently moved into a new apartment and we don't have the funds to take her to a new vet, I'm asking for $300 to help me take her and to get her whatever meds and anything else she may need (asking $300 because of fees, etc.).  Her name is Yuffie and she means a lot to our family, she's the most loving kitten you could ever meet and all she wants is to be cuddled. We'll be grateful for whatever donations we could receive. Thank you for your time.