I'm sorry about your sick Polish. My first guess is Marek's Disease based on her symptoms and age. Do you know if she was vaccinated for Marek's Disease (usually done at one day old by hatcheries- breeders don't always vaccinate). The vaccine isn't 100% effective so even if she's vaccinated she can still get it. Mareks often begins with birds staggering or limping and slowly progresses into paralysis. It is extremely common and spread through feather dander. Some people never have trouble with it, but some breeds tend to be more susceptible.
Unfortunately, there isn't really a treatment for Marek's Disease. Most birds that get it slowly waste away from lack of food or dehydration, or internal tumors kill them. Some people have experimented with herbal remedies like curcumin or St. Johns Wort, with varying success. I suggest taking a look at this extremely informative article on Marek's Disease:
The Great Big Giant Marek's Disease FAQ You may also want to check out the St. Johns Wort thread, if you want to learn about that "treatment" (doesn't work for everyone):
St. John's Wort
Alternatively, your Polish could have a neurological problem, possibly caused by a vitamin deficiency. If this is the case, you're doing all you can by using those vitamins. It could be weeks before you'd notice a difference.
A few last thoughts: check her eyesight. A blind eye could be making her wobbly and unsure, especially when around other birds. It's probably not the case, but it is good to check everything. Also make sure that she doesn't have any mites or lice since those can really sap a bird's strength, causing weakness which can lead to trouble walking.
Best regard to you and your bird!