100% sure its dropsey, I've lost 3 females in the past month due to dropsey. I lost 2 in 4 days & one a couple days ago.
they basically were doing exactly the same as yours (bloated, floating at surface, arched backs, raised scales, pop eye) unfortunatly the other day when i lost my recent female, she was there one minute & sank and i guess just didnt have the energy to surface again for air.
To be honest & im sorry to say there is basically nothing u can do, apart from seperate her to hospital tank & treat her best u can & treat the tank she came from aswell with a course of medicine to stop anything happening to other fish, although my aquarium said it isn't something that spreads, but hey i lost 3 fish to it.
i tried seperately of course during my dropsey disaster, melafix, salt & octozin etc & they had no effect in improving the condition.
Dropsey i heard is something you have to catch early (whenever that is) because once it sets in too far there's no way back. Yours im sorry again to say looks like its there to stay.
Don't get me wrong there may...just may be something that cures it but i had no such luck, ive researched it alot & no result so if u do find a god send cure please let me know.
sorry to be barer of bad news, i hope something works out.