How much room do they have, and what is she feeding them? Do thry get outside to roam around in a large area? Hens do not need a rooster period to keep them from pecking each other. Vent pecking is caused by a number of possible things. Overcrowding (less than 4 square feet in a coop and more in a run,) not getting outside to free range where they can get away from each other, not enough protein in the diet, agressive breeds, too much light in where they lay eggs. They can suffer a prolapse where red tissue comes outside the vent, and others may go into a frenzy pecking the red. I would recommend feeding a good balanced 16-20% protein feed as the biggest part of their diet. Your friend should spend some time with them observing their behavior. Remove any injured birds and separate them. Look for a bully, and separate her (or him.)
Here is a good article pointing out possible reasons for pecking:
https://poultry.extension.org/artic...ibalism-in-small-and-backyard-poultry-flocks/