Reproductive problems are not uncommon in hens over the age of two. Modern laying hens have been bred more for heavy egg production than for long lives. Many birds sold as Rhode Island Reds are more 'production reds' particularly if they are hatchery birds. I've had a pretty high percentage of reproductive problems in the ones I've had. Breeds considered 'heritage breeds' that come from reputable breeders who breed for standards rather than egg laying tend to have a lower percentage of problems over all, but it can happen in any of them. I agree, that since she's no longer laying, and the abdomen seems bloated, it's likely a reproductive problem. It's often not known exactly which one until a necropsy is done since symptoms can be very similar. I leave them with the flock until they are obviously feeling unwell, not eating or drinking, isolating themselves, or get attacked by the flock (the flock will often attack a sick or weak bird, it's survival instinct to drive a weak member out that might draw a predator). At that point I euthanize.