I just talked to the vet and she did pee overnight (phew!). He said she doesn’t have anything medically-treatable, but she does have crystals in her urine. The best treatment right now is to change to a special food (to help prevent crystals) and get her to drink more (by adding broth or water to the food). Part of me is glad it wasn’t something more serious, but part of me wishes it was something that could be fixed with a week’s worth of drugs.