The sooner you start treatment the better.....I would go ahead and get her in a small QT container and start the 100% daily water changes with fresh dechlorinated water of like temp.
QT-did she come in one of those little cups-if so-these work great for a temporary QT container for treatments.
Its important that the water temp be within a couple of degrees between the new and old water with the water changes so you don't cause temp shock and always use dechlorinater with any new water added to the fish/tank.
The bloat-can you tell if her scales are sticking up or is it just her tummy
Epsom salt (Magnesium Sulfate) can be found at most stores that have a pharmacy department-you usually will not find it at a pet shop
For a 5gal tank I would look for a 50w adjustable heater and you will also need a thermometer.