From what I've heard, chickens frequently heal from amazing wounds.
If you can set up a heat lamp she can always get close to while she's regrowing feathers, that's one thing that would be a help to her.
If you think at some point that she's battling infection & you want to give her an internal antibiotic, as well, Penicillin or Amoxicillin would probably be the best one for a wound infection. If she has any tears in her skin, rather than stitching you can Super-Glue them back together. Really! It can work very well!
Putting obstacles around for chickens to run around & hide behind could help some for future reintegration if you want to do that later. Here's some info I wrote before about that:
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You can put some obstacles in the coop to help out chickens that are getting picked on too much. These give the chickens something to hide behind, jump onto and run around while evading attacks from other chickens.
***Always be sure no blocked-off or dead-end areas are created where any chicken could get cornered.***
Sacks of feed, buckets, additional perches, trash cans, etc. can be useful.
Window frames (with either glass or wire in the middle) leaned against things can also be excellent for a flee-er to run behind and be protected yet be able to keep track of aggressor's travels. Window frames are even better if you can nail them so they are stand vertically and are at 90 degree angle to the wall. Then a fleeing chicken can also have the option to jump up and perch on the top edge to escape, and pursuer can't immediately chase her if she jumps down on the opposite side.
Lower-ranking chickens also appreciate shadowy, cluttered areas where they can hang out and not be noticed as much.
It helps to put food & water in some of these areas so less-dominant chickens still get plenty to eat and drink.
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I'm so sorry your pullet got hurt.
Established hens can be so crabby with newcomers sometimes.
Best wishes!