I know you mention her crop is empty, but I would re-check that again.
Photos of the poop in natural lighting would be good.
In addition to treating her as suggested in previous posts - consider a crop/digestive issue if she's acting like she's dry heaving. She may have a partial blockage.
This article will get you started - yes - the treatment(s) in this article can be used in conjunction with treatment for worms and coccidiosis.
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/