Start off with 1 tsp per gallon for two day's and then up to 2 tsp. You can use 3 tsp np, but if her poop turns normal after a few day's then there's no need. Once her poop is normal again then the parasites are out, do daily water changes and replace the salt that you've taken out.
So if you remove 2.5 gallons of water from the tank and you're using 1 tsp per gallon, mix up 2.5 teaspoons when you go to add the new water to the tank. That way you're keeping her at 1 tsp per gallon. Make sure you dissolve the salt before putting it in the tank! I use small plastic cups and use some tank water, measure out 1 or 2 teaspoons at a time (smaller portions melt faster is all) and mix it up and slowly add to the tank over half an hour so she can get used to it. Salt makes heat while it dissolves so it can hurt your fish if you don't dissolve it first is all.
So do a schedule like this:
Day 1: add 1 tsp per gallon of ES.
Day 2: Do 50% water change and replace salt that you took out.
Day 3: Do 50% water change and replace salt but also add more to make a total of 2 tsp per gallon of ES.
Day 3: Do 50% water change and replace salt that you took out.
Day 4: Do 50% water change and replace salt but also add more to make a total of 3 tsp per gallon of ES if needed.
And so on, but after 3 tsp just keep doing water changes to get rid of parasites and do not increase salt, just replace. You can do this up to 10 day's and then let her rest if she's still showing white poop but she should be fine by then.