I live very close to an emergency veterinary service that is open 24x7 every day of the year but when I asked them to keep a kitten with a severe URI they said he was still better off at home and they refused to take such infectious cats unless their lives were in immediate danger. So, your vets may refuse. My regular vet keeps infectious cats in their restroom (heated and large) to protect their other sick clients. From what I have been told over and over as I've dealt with URI's in many cats, there is nothing they would do beyond what you are doing now. She's actually better off in your home, frightening as it is for you, and I do empathise with you.

Did the vet take blood to find out why Emily has lost weight? My thought is that Emily has an underlying illness, such as early renal failure or hyperthyroidism, that has caused the weight loss and made her more vulnerable to infections.

Keep doing what you are doing, especially the force feeding even though it's very distressing and scary when they are mouth breathing. I've always used AD, is what you are using from the vet?