Go out tonight and feel her crop along with a couple of other hens. Run your hand down the right side of their breast. You should feel a lump or bulge where the crop is located. This is food/water they have eaten and will process overnight while roosting/sleeping. You'll probably notice each hen has a different feel and fill.
Go back out early in the morning before the hens eat/drink and re-feel of the crops, the area you felt the night before should be empty or flat feeling. If your hen's crop still feels like it's got fluid or food in it, then begin treatment.
The reason I suggest feeling of several hens is so you can do a comparison. Sometimes it's easier that way.
Photo Ref
Go back out early in the morning before the hens eat/drink and re-feel of the crops, the area you felt the night before should be empty or flat feeling. If your hen's crop still feels like it's got fluid or food in it, then begin treatment.
The reason I suggest feeling of several hens is so you can do a comparison. Sometimes it's easier that way.
Photo Ref
