The large fluid filled cyst thing on her breast - that's most likely her crop. That means she's drinking a lot and it's backing up. Her fluidous poop is just that - a lot of water that she's putting through.
Birds don't normally pass water through in their droppings like you're seeing. Their 'urine' is actually passed in the form of solid white urates, eliminating the need for and weight of a fluid filled bladder. You may be seeing some of that in the watery fluid.
First, open her mouth and take a good smell. If you smell souring, then she might have an impacted crop. The pendulous mass at her chest, being most likely a crop, shouldn't hold water like that - not for long. Is it possible she got a foreign object? Does she have access to grit if she's been allowed out on grass, especially our nice new spring grass that chickens love to choke down?
For the moment, I would remove the scratch and other solid foods until you can verify that she's not impacted. Crumbles will dissolve and move, as a slurry, through an impacted crop more readily than will grains (which require the action of the gizzard, later in the system, to break them down into nutrition.) Grains sitting in the crop will sour. Crumbles will too, but as I mentioned they're a little more likely to pass through to a place where they can be absorbed.
Also, are you having heat now that you didn't before? IS she showing signs of heat distress - the lifted wings, panting, etc? Has she had access to anything excessively salty that she might have eaten?
Is she showing any signs at all of respiratory problems (wheezing while breathing, sneezing, etc)? You might have to watch her on the sly for a good period of time to get her to relax and do what she's doing normally. Sometimes increased thirst is a sign of respiratory illness, or other illnesses such as black head. Check her carefully for anything out of the ordinary (including parasites on her feathers/skin), check her weight (is her keel prominant), etc.
I would probably separate her into a place where you can really observe her droppings, as you have been. And her food intake. And to keep her away from grass and other solids.
let us know about the crop, etc, and anything else you may discover. By the way, you might be able to get her to eat some boiled egg yolk that has been moistened with water so that it's not so solid. You can also mix some crumbles into that to get nutrition into her, but I'd wait first to see if her crop goes down. If you have to get her to eat tomorrow (unless she starts fading today) you have that as an emergency backup.
Hope this helps to start you off.
