The Corid won't hurt her, but it will not treat worms. It will only treat Coccidiosis.Her poop is completely liquid today, almost looks mucus-y. I haven't seen any storms in her poop and I've also never dewormed my chickens. I started her on corid yesterday, just in case.
Did the vet not run a fecal float to see if worms are part of the issue? If not, then if you want to deworm her, use Safeguard Liquid Goat Dewormer (Fenbendazole). Dose is 0.23ml per pound of weight given orally once a day for 5 days.
I know it sounds like a lot, but often a hen may have more than one thing going on. Once condition or illness can drag the system down and allow other issues to escalate as well.
I would first treat infection and crop as suggested. See what happens.