Update: Her mood and actions are unchanged, but I did notice she has some red dots down her legs. She's not acting like they are mites or anything, but I checked her sister and her legs don't have the dots, so maybe it's a clue?
She's stopped eating mostly and starting to lose a little weight, but I did another checkover and can't see any causes. She has a few new feathers coming in near her abdomen, but I think it's from when she went broody a couple of months ago. I'm wondering if I should just let her rejoin the outside and see if that helps her mood? She's just sitting at this point.