I wouldn't go to this vet anymore. Try to treat Coccidiosis first. Since she may not drink well, you can do corid drench: https://www.backyardchickens.com/threads/corid-oral-drench-instructions.1211991/No, vet didn't check for worms.
If you don't see any improvement after 3 days. Try to deworm her to see if it's the issue. https://www.heritageacresmarket.com/how-to-deworm-chickens/