There's hope for her yet. I have isolated her in a small floating tank (bigger than a fry hatchery) until I get my hospital tank today so that I can ensure that she gets all she wants to eat. I have been feeding the fish with daphnia, brine shrimp & bloodworm (all frozen, and it's 'no holds barred' when the bloodworm goes in hence the seperation) plus algae tablets. She is now swiming with dorsal raised & tail fanned a lot of the time and she too loves the bloodworm. Before seperating her she was only getting 1 or 2 bloodworm, now it's 5 or 6 and she seems to be putting on a little bit bulk at long last (it's only been a couple of days be the difference is noticable). She was a loverly fish before all this started & even though she's not well I don't want to lose her. Now if she was really bad I would consider ending her misery but she has never been that bad.
I've been on holiday the last couple of week so have been on the net for hours looking for info on a possible cause but have come up with nothing that matches her symtoms other than stress (she was bullied but that stopped when I gave the swordtail to the lfs).
Well it's time to give her more bloodworm, 1 at a time until she stops eating them straight away then 1 more which she usually eats 5-10 mins later, then what's left gets 'thrown to the wolves'.