Okay, so my feed store didn't have Save-a-chick, so I got the polyvisol, no iron. It has E and B but no selenium. So, should I get some selenium, and if so, in what form? Maybe a food high in selenium? I'll research that.
I got some antibiotics, but I got the wrong thing, but now I know not to use it.
I just got back from the store, so haven't given her anything yet except for egg, french toast (!), and starter soup, and she already seems better. She does drink on her own and is interested in food and is eating. So I'm not having to give her food and water via dropper. The water level in her drinker has gone down significantly since last night and she hasn't spilled any. I hadn't handled them very much since I got them, and they'd run like a scary, chick-eating monster was after them, every time I'd cleaned and change water/feeder. She, however, now that she is separated, doesn't seem the least bit afraid of me and is quite content to sit on my lap for treats. Interesting. I run an animal rescue (mostly dogs and horses) so I know the rescued ones are the most grateful and willing. Maybe that's the case with her...
You all are being very helpful - I'm grateful! And so is my little girl 
[Edited 5 minutes after: First let me say that I found another thread on this and it is several pages long. And the responses/ solutions are so varied that it's quite confusing. I felt good about the polyvisol I just bought, until I sat down to read more and read this thread. 
https://www.backyardchickens.com/forum/viewtopic.php?id=97121&p=1]