Have you seen her poo at any point? If so, can you describe what the poo looked like?
Is she still eating?
Are her gills moving at the normal rate?
How long has she been in the tank?
What other fish are in with her, how many and in what size tank? If you have other gouramies as well, also let me know what sex each is.
Dwarf gouramies are particularly susceptible to internal bacterial infections. This is likely to turn out to be the problem. Constipation is also a possibility though.
What you can do is, if she's still eating, fast her for a day, then feed her some crushed, de-shelled green peas. If she won't eat peas, try frozen or live daphnia instead. Both should help clear her system a bit and help her to recover - only if the problem is constipation though.
While you're at it, do you have a spare heater somewhere? You can use a bucket or plastic storage-type container or tupperware as a makeshift hospital tank. A cycled filter would be an ideal addition to the isolation tank but won't be necessary in this case. Then get yourself a powerful antibiotic and start treatment. Daily water changes will be necessary if there's no filter or, most likely, will be necessary anyway as the antibiotics are likely to kill off most of your biological filtration anyway. If you can get medicated food and she's still eating, that would be even better. What you should be looking for is something that'll treat dropsy or pop-eye as these are symptoms that usualy result from internal bacterial infections like those that dwarf gouramies are especialy susceptible to.
I have to warn you that they rarely survive and that you probably won't be able to save her if it truly is more than constipation. Having said that, it is worth a try and it is also in your best interest to take this as a chance to invest in a hospital/quarantine tank with a heater and small filter and start the antibiotic treatment immediately.