Do you have any way you can separate her from the others? Like in a portable dog kennel? I would separate her. Make sure she's in a warm, draft free, dark, quiet place. Stop all treats for the time. Get some polyvisol (without iron) drops and put them in her water. Encourage her to eat by wetting her Layena and mixing a tablespoon or so of wet cat food in it.
Separating her will accomplish a couple of things. First, if she has something contagious, although it may be too late, you might prevent spreading it. Second, you will be able to better monitor her intake and output - monitor her poop and compare it to the poop chart:
http://www.chat.allotment.org.uk/index.php?topic=17568.0 . Third, you can control her environment to make sure it stays dark for a longer time during the day so if she's having a laying problem, her body won't be encouraged to lay right now. And, fourth, you can more closely monitor her behavior.
Unless and until she shows more symptoms, I'm not real sure there's much more you can do. Do you have some "basic" meds on hand? Like a couple of different wormers, penicillin and syringes, etc??
That's some of the basics. NOW, if it were one of MY girls - and I think I am a bit aggressive when it comes to treatment so no pressure - I would be worming all of them. A lot can happen in a couple of months. Wild birds can bring in mites/lice/worms and other illnesses. I will privately message you with some info I keep on hand from dawg53. He's one of my gurus on here and I trust him implicitly with the health of my girls (and anything from CMV).
