My cat is having a hard time eating/drinking & coughs up phlegm.?

I had 2 cats, Sonny & Tags at 17 years old each. I say had because Sonny had to be put down on Friday and this hurt me more than ever as he gave me so much love, affection & fun over the past 17 years, but I know he is better off now as he was suffering the last few days and the vet said it was best for him and not much could be done for him at this time. Tags is also 17 yrs old and she just started to get sick where she has one runny eye and she can't keep food & water down because she keeps throwing it up... but it is mostly phlegm. The Vet took some blood test and then put her on an IV drip for a couple of hours to hydrate her more and then we picked her up. Next day, Vet called and said that she has hyperthyroidism and put her on Methimazole, a prescription medicine that she will need take for the rest of her life. She also got an antibiotic injection plus Clavamox drops to take to help her get better. Problem is....she has been on the medications for 2 days now and she still can't keep her food down. I am able to give her medicine by an eye dropper and she struggles with that, but I have been successful. I then bought some pill pockets and she LOVES them and is working to give her the pills, plus I've given her a few extra if she will take them. But I have tried to give her cat milk, tuna, chicken soup/broth, water, pasty cat foods, you name it. The Vet's office called this morning to check on her and I told them about this and they said that they will let the Vet know and he may return my call later....but they did recommend baby food (like chicken and rice or something like that). So I will try that too. Last night I did force down about 2 droppers of the cat milk. I am hoping that the little bit I got down her is doing some good and she will start to improve, but I am so worried about her. So far I have spent over $700.00 in the last 3 days. By the way...all of her other tests seem to be normal for her age and the Vet did say because of her age that they could not promise that she will recover. I just could not put both of my pets down, especially Tags since she has been healthy until just the last few days. I am wondering if anyone has experienced the same with their cats and can share some good suggestions, feedback or input. Please do not tell me to put her down...it is the very last resort. I know that she probably needs to go back to the Vet....but maybe I am not giving her enough time to respond to the medications. She is responding to me when I call her and walks around. This morning she was all excited for her food, but that changed after the first couple of licks. Thank you for your kind thoughts/suggestions....anything you have to offer is and will be most appreciated.