Sorry for your loss. Can you post a picture of her poop?
I'm sorry for your loss
What symptoms did you see in the one you lost? Was a fecal float test performed?
Although we mostly associate Coccidiosis being a problem in young chicks, it can be seen at any age. Warm, wet conditions are a breeding ground for Cocci and any chicken can become overloaded.
Since you lost a pullet due to Cocci, it wouldn't hurt to go ahead an treat your flock. Treatment is with Corid, which can usually be found at your local feed store and online. Corid is considered mild and generally safe when used properly. There is no egg withdrawal period since it's a Coccidiostat and not an antibiotic.
General symptoms include lethargy, going off feed, diarrhea with mucous or blood, loss of balance and having a puffed up appearance.
If you have a vet that can perform a fecal float test on fresh poop samples that would be best. If you happen to lose another to similar symptoms, then sending the body to your state lab would be a good idea. The information you receive will confirm whether Cocci is the problem or if there is another underlying condition that needs to be addressed.
FWIW - Corid dosage is 1 1/2 teaspoons Corid powder per gallon or 2 teaspoons of 9.6% Corid liquid per gallon. Give for 5-7 days - make sure this is the ONLY water available during that time period. Mix a fresh batch at least once a day.
After they finish treatment offer some poultry vitamins and probiotics/plain yogurt.
Keep us posted.
Here's a fairly good list of symptoms:
http://www.thepoultrysite.com/publications/2/Coccidiosis Management/43/symptoms-and-diagnosis/
More Cocci info:
http://www.merckvetmanual.com/mvm/poultry/coccidiosis/overview_of_coccidiosis_in_poultry.html
As mentioned above, it can happen to any age bird and can be rather common in certain areas of the country or world. 
Corid is a fairly mundane substance, acting like a Thiamine blocker which the Cocci need so badly to survive and breed on. It doesn't effect the bird much if used properly. And definitely, as Wyorp Rock has mentioned, use Probiotics after a course of Corid.
AnotherI am so sorry for your loss and you are having to deal with this.
Every flock is going to be different, and each strain of Cocci effects different parts of the intestinal tract. My adult birds have had a few cases over the years, picking it up while free ranging as our wild birds carry Cocci pretty severely. The cocci I have to deal with seem to start out in a particular way. I have found that one of the first signs in my flock is a LOT of white urates on the poop. I mean an excessive amount of urates. Urates will stain the butt feathers as well. The next symptom I see is a slow crop and mucus in the poop. Only one time have I ever seen blood in my birds poop with the species of cocci I have in my territory. Sometimes blood WILL be the first symptom and it can look like chunks of tomato in the poop or streaks of blood on top of the urates.
BUT...when in doubt, run Corid through them. It's never over reacting when lives are at stake.
