Unfortunately there's not much good news in the saga of my sick chick. I've been giving her vitamins for about 4 days and there has been no improvement; in fact, she seems worse and is having the seizures more often. Yesterday I started giving her tetracycline (in her water) as well to see if that helps. I've decided that if I see no improvement by Sunday I will be sending her to the Great Henhouse in the Sky. My neighbor, who is a vet, said he could do it humanely for me for free... It has become somewhat of a burden, especially with the visiting parents, toddler, etc. etc. Lately she has taken to knocking over her water in the middle of the night so every morning I have to clean her cage before I go to work. (If some kinder soul would like to adopt her and see what they could do, I'd be grateful... but I really think it's pretty hopeless at this point).
In the event that I do send her on to a higher plane, I will be looking for an older chick or young hen to replace her - preferably a buff Orpington or a barred rock. Anyone have an older chick available? Thanks for everyone's support and advice during this ordeal!
...And I got a reply right away from someone who is actually going to trade me a healthy, four-week old barred rock for my sick, four-week old barred rock. She's willing to take on the hard cases, and she has chicks to spare. Yay! Gotta love the internet.