If you have other egg shells, also you toss those out into the coop. Chickens eat them plain and use the calcium to build their own eggshells! Hopefully your next eggs will be normal within a couple days or a week if they are getting sufficient calcium. They should become normal size in a month or two.
What breed is she?
They end up on buffets or in precooked premixed products . In the bottom of the oyster shell bag there will be dust . Get the dust a sprinkle it over their feed . If the oyster shells are large make sure they have access to grit . Or grind them down smaller . Make sure the crumbles you switch to are similar to the starter grower you've been feeding . Plenty of clean fresh water and you have given them all they need to make the perfect egg . Up to them to complete the process . So just how much did that first egg cost ?

