At this moment-you don't have to make a decision.
Find out what you are dealing with before you stress yourself. Treat your girl and keep her isolated.
It'll be OK-she may have something totally different going on than the chicks.
Something you should be able to do is call the State Vet in...
Honestly, it all depends on what you're dealing with.
If you lose one, seriously, get a necropsy done on it-then there can be no question and you'll know exactly what to do that is best for you and your flock.
It would be a hard call for me to make-I love my birds and I would probably close my...
A lot of the respiratory illnesses do cause them to be carriers-NOT ALL.
I would never tell anyone to cull their flock-that is a 100% personal decision.
If you keep your flock closed(don't buy/sell birds) there is no reason to cull.
You're not even sure if it is a respiratory illness-I certainly...
OK, I am going to give you my BEST guess with your girl and that's all this is, is a guess.
Now, let me start by saying that IF it is a respiratory disease, some of them, despite the fact that you treat her and she gets well, will cause her to be a carrier of this disease the rest of her life...
OK-is her comb pale or turning bluish purple?
Is her comb turning purple/blue? This would be sign that she's no getting enough oxygen.
Has she been laying regularly(or is she of laying age)-trying to make sure she doesn't have an internal infection from an broken egg(egg peritonitis).
You said...
MissLydia stated this a few posts back about gapeworm.
"Also check for gape worm by using a qtip and putting it a little ways down its mouth and see if anything comes out on it you have to go a ways into the throat. From what I've read the worms are red and have like 2 heads. their small."
She...
Do you have her in the house? She needs to be in the house where it's quiet and pretty dark so she'll stay calm.
Did you feel her crop and check down her throat for gapeworm or possible wet pox lesions?
The crop shouldn't be hard or squishy.
The link below shows where the crop is located on the bird.
http://poultrykeeper.com/chickens/health/digestive-system-chicken.html