My hen either has sour crop or coccidious.

[Wyorp Rock]

No, I would not try to vomit her.

What did the vet originally give her and diagnose her problem to be?

I would take care giving liquid oil since they can aspirate. I give mine hardened pieces of coconut oil, they love the taste of it and will usually just eat it right up.
If the crop is squishy, then she may have sour crop. You can try treating for that to see if she improves. Often a crop issue is symptom resulting from an underlying condition - in laying hens reproductive disorder can be common. Other conditions like infection, worms and coccidiosis can also cause the crop to slow in function.

Here's some really good info on how to treat crop problems -I use these methods myself.
https://www.backyardchickens.com/ar...w-to-know-which-one-youre-dealing-with.73607/