Prolapse is when the tissues that are supposed to be inside a body opening protrude from the opening. They must be kept clean and moist so they don't dry out and returned to the inside of the body cavity if the bird is to survive. Keep your bird in a dog crate where the other birds can't peck at her damaged tissues.
Please post a picture after you get her cleaned off. Do not give her a complete bath. You can set her in a basin with a little warm water in it and pour water over the damaged area but don't get her wet all over. Cover the protrudung tissue with Vaseline, Preparation H, or triple antibiotic ointment that does NOT have pain reliever in it until you hear from one of the following Educators for more detailed instructions.
Is she a silkie? Has her prolapsed vent been pecked at? As said, keep the prolapse from drying out, and an ointment or honey will help to keep it moist until swelling goes down and the prolapse may go back in. Does it feel like an egg is stuck, or has she just been straining? A human calcium tablet given orally may be helpful. I would offer some fluids up to her beak. Keep her separated and away from flies until the prolapse stays in.