Hi there. I'm sorry I got to this late. Poor mama!
First, when the pullet was up there for a while, she wasn't getting nutrition, hydration, etc - likely was very stressed, and stress is in itself enough to make a chicken stressed.
I just want to clarify - was there any chance of actual injury? It's possible she has an internal injury that isn't obvious.
Also, is she of laying age?
First thing I would do would be just leave her there in the quiet place, and offer her easily digested and nutrient rich food: the water melon you offered (for water), water with vitamins/electrolytes are awesome for this sort of thing. Boiled egg, a little yogurt.
I'm a little concerned about the droppings - is it possible that instead she just went in there after having had something toxic to eat? Could she possibly instead have gotten into any wet or soured feed/grain, compost, maggots, mildewy anything, old feed, algea water, mud, etc?
Also since her droppings are the way you've described, if you have any applesauce I'd give her a little of that, a few drops of molasses, her pellets/crumbles, a little yogurt, and water in a wet mash. These are good things to have around. (I buy babyfood applesauce because it's cheap and individually packaged and lasts ages in the cupboard). Give her a *one time* feeding of that to clear out whatever is making her droppings smell so bad.
If she's a laying hen, I'd also investigate the possibility that she had an egg broken in her.
I'll wait for your reply, but mainly right now the goal is to get nutrition and hydration in her, preferably with some vitamins/electrolytes in it. And see what tomorrow shows.