If it has stopped bleeding, can you spray the vent with anti-bacterial and try to look closer? Is there a tear or sore? Look for bugs or clues about the injury. Can you inspect under wings and legs to look for mite bites?
Do you have a Rooster?
Is the roost set up so backsides might get pecked?
If it is pulsing, and she seems unable to pass a poo or egg, have her gently stand in a Warm Epsom Salts bath, with your hand on her back, as she relaxes, use gentle pressure on her back so she lowers enough to cover her back side/vent but bit all her feathers or back. This may help her to relax and stop straining if she is doing that. 20 mins or til water begins cooling, and have a kennel/towel ready in a dark area, if you can, to let her heal a bit.
If she's reached laying age, squatting, red comb, add some calcium and switch to Layer food, if you haven't yet. Some yogurt mixed in may help her fight a bacterial imbalance and accept new food. If no Corid for a while, maybe treat the flock for Coccid - or parasites if poo indicates clues, or if they free range.
Pics of poo and vent might get a better answer. Others may have other ideas. Ignore them, IMO, if they say to put your finger inside to look for an egg. Good Luck.