If she's crushed an egg at her vent or further into her vagina you need to wash the remnants out. There are possibly pieces of shell and other rotting debris that can encourage infection.Am update. She came out of the coop of her own accord. Not with as much gusto as usual, but she's pecking and drinking. Crop still has a little in it, but she'd pooped more overnight. Runny again, but at least it's coming out.
I did try to get a good dose of water in her, before I have to leave her for the day, but she fought so hard it was just more stress than anything else. I have seen her drink, so I'm happy to leave it at that for now. I've given them some very wet ff (they get a small daily portion), just to help get more water into her.
Fingers crossed we're over the hump.
Funny thing; she's a bit of a bully to the two below her, but obviously she's not bothered them over the weekend. Maybe I'll see a bit of a change, at least for a while.
You'll need a large capacity syringe and the touch of a midwife.
Fill the syringe with luke warm water; do not add any chemicals. Squirt the water into the hens vent. You need to use a lot of water in this flushing out process, a quarter of a pint is the volume I have in mind.
You can insert your finger into the vent and carefully feel for any bits of shell and egg that the water hasn't flushed out and very gently scrape any bits out with your finger.