If you have an extra airstone I would add it.
DAY ONE
Today, before your first dose of medication, I would do the water change, maybe 80%, and using 3 drops per gallon on this first water change.
Now dose the tank with the antibiotics.
I would take a cup of this new water from the tank, add 5 level teaspoons of salt and almost bring it to a boil in the microwave to make sure the salt is dissolved. I would wait until this cools and then slowly add this about a fourth of a cup at a time over the day. (over 12 hours) Now the tank is at 0.1% salinity.
DAY TWO
Tomorrow, 24 hours after the first dose of medicine, I'd take out at least 4 gallons, or 80%, but I would get the replacement water ready first before you remove any.
You want her tank again at 0.1% salinity again before you increase the salinity, so in this replacement water I would add 4 teaspoons of salt, the amount that has been removed, (make sure it's dissolved), and I'd put the amount of Prime in the replacement water for the 5 gallons the tank holds, which is 0.5mL.
You have now got the same .1% salinity in the tank as the day before at this point.
Again, remember to get the replacement water ready before you siphon off the water in the tank, this way the fish isn't stressed by sitting in an extremely low level of water in their tank for more than just a moment. I add the water back quickly, but gently of course, as soon as the water has been siphoned off.
Now, that the tank is full again and at .1% salinity, remove about a cup of this tank water and dissolve another 5 teaspoons of salt and thoroughly dissolve it. Go ahead and add the next dose of antibiotics to the tank and slowly add the cup of salt water over the next 12 hours.
Now the tank is at 0.2% salinity. I think that's the degree of salinity I'd stay with.
Now dose the tank with the antibiotic.
DAY THREE
Today, 24 hours after the last water change and dosing of meds, get your replacement water ready again. Add 8 level teaspoons of dissolved salt to the replacement water (to replace what was removed with the siphoned off water). This time I would do 1mL of Prime in the replacement water. This is the usual amount for a 10 gallon, but that's OK... you can even go 5X the usual regular dose when you have ammonia or nitrite spikes, so this won't hurt at all.
EVERY DAY UNTIL FINISHED THE COURSE OF TREATMENT
Do everything as on the third day until the treatment period is ended. Continue to feed only the medicated food, except you may want to feed one nuked pea to help keep her from getting constipated.
Test her water at the end of each treatment day and if you see traces of ammonia or nitrite, add about .5mL of Prime to her tank to carry her through the night safely. This won't hurt.
Do a gentle vacuum of the substrate as you remove the tank water, if this doesn't stress her too much. Don't stir it up vigorously, but just be gentle.
I'm going to recheck the recommened length of time for those meds and be right back.