So
the vet apt is today, I found an exotics vet about an hr & a half from me that was willing for an additional fee of course to see her before December. All local vets wouldn’t take new customers until January.
She’s alive & eating good still doing the 1ml of niacin a day & supervised swims twice a day but she can’t stand at all.
I'm happy to hear you found a vet.
Generally, the major cause of lameness in waterfowl is due to a deficiency in niacin (B3), since you're not seeing much improvement with the B complex, it seems the problem is not related to niacin, although, with a bird this age, improvement may take several weeks since their legs are more 'set in-place", and harder to correct.
Besides niacin problems, you often see septic arthritis, usually in young birds. Podermatsisis, Toxicosis, Mycoplasma, or trauma to the legs, among many more. I hope your vet is able to figure out the problem. Let us know how it goes.