I'm sorry you lost one of them
You're right, poor girl has a prolapse and looks like maybe a bit of damage from picking.
Are there any maggots on the exposed tissue? Hard to tell, but let's hope not.
If she's lethargic, then getting her in a soaking tub may put her over the edge. I'd clean the prolapse either by soaking in a warm epsom salts bath or spray it with saline, diluted chlorhexidine (Hibiclens) or betadine. Keep the tissue moist with honey, sugar pack, coconut oil, triple antibiotic ointment...whatever you have on hand, the goal is to keep that exposed tissue from drying out and becoming necrotic.
This is when you do want to separate her out so her vent doesn't get picked at. Place her in a kennel, crate, etc. on clean dry bedding. Puppy pads in your kennel or crate work well, they are easy to change out and clean up is convenient.
I'd work on hydration. Get her drinking. She needs extra Calcium. You can find Calcium Citrate with D3 at
Walmart, CVS, etc. give her 1 tablet daily. Just open the beak, pop it in and let her swallow. If you don't have the Calcium Citrate, 1 TUMS daily will work too.
Calcium helps with retention, so hopefully as the swelling goes down, she will be able to pull in the tissue herself. Or you may need to assist. It can take a few days for this to happen, so just do the best you can with keeping the tissue moist and sprayed clean.