Which one? LOLKind of.
If she's got some bloat or swelling in the abdomen below the vent between her legs, I would suspect a reproductive disorder. Peritonitis, cancer, Internal Laying, etc. can be common in laying hens. Sadly, there is not a lot that you can do to treat a reproductive disorder.
Monitoring the hen and seeing that she's eating/drinking, checking to make sure her crop is emptying overnight, looking her over for lice/mites and getting a fecal float to check for worms are about all that you can do.