I'm glad you were able to get the results back.
Very sad indeed. Unfortunately cancer is quite common in laying hens as are the resulting symptoms you have described.
Here's the article again for treating the crop.
She's an adult hen, so give her 2 teaspoons coconut oil daily. That's in addition to the yeast medication.
https://www.backyardchickens.com/articles/how-to-treat-sour-crop-and-impacted-crop-and-how-to-know-which-one-youre-dealing-with.73607/...
She needs to be given some fluids if she's not drinking on her own. Tube or syringe fluids into her. If you are going to the vet, have them show you how. There's loads of Youtube videos about how to tube and syringe fluids into chickens.
Offer her wet mushy feed or you can tube a little wet...
If her crop is not emptying then I would begin treating her for that.
Often there's an underlying condition or illness that is causing the crop to slow.
Did the vet run a fecal float to see if worms are part of the problem...