You said you saw worms in her droppings. Did you by any chance get a picture of them?
I think if this little pullet had coccidiosis and a worm load, it was just too much for her to overcome. I'm sorry that you lost her.
I would certainly do a preventive course of Corid for the rest of your flock. The dose is 1 tsp of Corid to a gallon of water for 7 days. Change the water daily and ensure this is the only water they have available to drink.
After that is over, I would collect a combined fecal sample and submit it for a fecal float to your vet. If they find a lot of worm eggs, you can deworm with an appropriate dewormer.
After you are finished with the preventive Corid dosing, I would offer the flock some probiotics or a little buttermilk in a wet chicken mash to help their guts heal.
What exactly are you feeding your flock?