With any antibiotic once you start, it is not advisable to stop unless it is life or death because it presents issues with problematic resistant bacteria in the future .. this is pretty much why most people do not use Amtyl anymore. :\
It is not nearly as effective as other options available..
I think isolating her and offering a hospital cage with warmth, her favorite foods, clean water, etc., would have been the best first choice - and then go from there.
Since you've started the antibiotic, unless she starts to crash in the next few hours it is best to continue it for the full course of treatment.
Yeast is a gradual disease - a "long term" killer, meaning they won't keel over overnight.. but it is also usually secondary; if a healthy adult bird succumbs to yeast there is usually an underlying problem that should be analyzed (bacterial, protozoal, parasitic, etc)
I would continue with the abx and then follow up with a probiotic

If she gets any worse, let us know..