Is the parasite treatment not working?

Question
I bought 6 female bettas a week ago. Almost immediately i noticed one had very clamped fins and stayed near the top in a corner. She would sometimes freak out and "shiver" and dart and scrape herself on objects. I figured this sounded like gill flukes; or some sort of parasite for sure, though nothing visible. She also has faint white-ish patches on her head that i can only see in the light at certain angles, kind of like excess slime coat, but in patches. Maybe fungal or bacterial? Or in response to parasite irritation?
I put her in a 2.5 gallon hospital tank (with another submissive female for company and so she wouldn't get used to being alone), and put in 1 tsp/5 gal of aquarium salt, and started treating with Tetra's Parasite Guard, a combo of Praziquantel, Dflubenzuron, Metronidazole and Acriflavin, since i'm not sure what parasite i'm dealing with.
The instructions say to dose every two days after a water change. Today was her third dose, so her fifth day on the meds (i'm doing 100% water changes every two days before re-dosing).
She seems as bad as ever. Hardly swims at all, just hangs at the top or lays on the bottom, almost on her side sometimes. Her fins are very pinched, and she is pale with horizontal stripes. If i wake her up once a day to see if she is still alive she freaks out and shakes and flashes everywhere and stretches her gills open. The other girl in there with her in ok, and doesn't bother her at all.
I've read that flukes can be really irritating before finally dying. But i'm just wondering, how long is this suppose to take? When will she start getting better? I don't want her to die! Should i do something else? I didn't think it should be taking this long.
(Since they all came in the same batch and some of the other girls also had clamped fins, i'm also treating the big tank with the same meds. None of them are getting worse, so i hope it's working for them, though some still have clamped fins sometimes. Even the pleco is fine, so the meds can't be that hard on them. But then, is it strong enough to kill the parasites? If i have to start a different treatment in the hospital tank, should i also in the big tank?)
Please tell me what to do! Should i wait some more? Add something to the treatment? Try something else intirely? How long until the fluke life cycle is completelly ended?

(Also i have large drift wood in the big tank. Does that affect the meds in any way? Does it absorb it, leaving less in the water to treat the fish? There is none in the hosital tank. But i didn't want to treat with something that would stain the wood. But if i have to take it out i will.)
Thank you!

Answer
Hi Joleen,
 Hmmm.. that is a tough.  First, because you have a catfish in the big tank be very careful about any meds you put in there; catfish are extremely sensitive to medications.

  There is not set time that it takes a medication to cure a disease.  The reason is that in some cases the disease keeps reinfecting and it may take a while to competely get rid of it.  This is particularly true of parasites that have complex multistage life cycles (such as ich and many flukes).

Personally, I would not have that other fish in the hospital tank. You risk it getting infected. She does not need company and in fact, "company" may contribute to her illness.  

Bottom line: I would isolate the sick fish and keep treating her.

-- Ron Coleman
  rcoleman@cichlidresearch.com
  Cichlid Research Home Page <http://cichlidresearch.com>