I just want her to be better!
I feel SO horrible that I didn't start the new antibiotics earlier... now I feel like I am back to square one with her health and three weeks have gone down the drain!
First of all, what is the new antibiotic you are using? Is it for cats? I ask because I've never heard of a raspberry flavored antibiotic for cats. And is that dose right?
Second, most antibiotics come in a pill form and a liquid form. Despite what vets think, pills often are easier to get into a cat than a foul tasting liquid. Open mouth, pop in pill, give treat. I'd call and ask for pills.
Third, if the amount she is to get seems to large for her to swallow at one time, give her a little, wait, give her more. Make sure you are giving this near or at meal time so the antibiotic doesn't totally mess up her digestion. You don't want a sick cat who is not eating! I would not hold her mouth shut to keep it in. She could choke on it.
As for three weeks down the drain, patience! Most kitty colds are viral. Antibiotics are used to prevent secondary infections, such as pneumonia or sinusitis. Antibiotics will not stop the cold -- the virus needs to run it's course which may be 1-4 weeks. The best thing you can do is to keep her eating so her body has enough energy and reserves to fight off the virus.