I'm hoping, given the other factors I mentioned, she can formulate an opinion.
Poopy butts in my flock have been due to so many things, cancers, worms, repro issues, infections, or a combo, so it's impossible to guess without more info. Your hen sleeps in her bedding, so maybe she sat in a pile of poop? That would be they best case scenario. What concerns me is that you commented the her feathers looked off. Since most of us aren't going to take our birds to a vet, we have to learn how to be our own vets, so think about how a vet might go about treating a chicken. Pretty sure most would start by just watching it, then they would weigh the bird and do an exam. That exam would include checking mouth, eyes, ears, vent, palpating belly, etc. Poop... All bird vets will want to check the poop. Since most of us don't have what's need to check it microscopically, we have to find similar looking pictures online and guess.
There is a method to my madness, so I say place your wife's food scale on the bathroom counter, catch the hen, turn off bathroom lights and place bird on scale. Once weighed, do a thorough exam and make note of how fat or thin she feels. If possible, place in a crate on towel of newspaper for poop sample.