Blu-kote. Should be available at your feed store. Our roo was a little overagressive when he was first with the girls, and he nearly scalped his favorite girl when she tried to get away. We kept her in a box in our laundry room for a few weeks, spraying the blu-kote on her regularly as directed, and she healed up well.
Once she was healed, we were ready to put her back with the others, but we first let her free-range outside the run for a little while every day for a couple of weeks, then would put one of the less aggressive hens out with her, then gradually let them all out and after a little while of free-ranging put her in with them. They pecked a teeny bit off and on the first couple of days, but now they leave her alone.
If you don't want to babysit her while you free-range her outside their pen, if you've got room in the coop, putting her in a dog crate inside the pen or run with them so they can get more used to her should help, after she's healed.
Chickens heal amazingly well if given the chance, so get some blu-kote on her or maybe some antibiotic ointment, you'll have to look it up on other threads to make sure it's chicken safe, but lots of people use that, too. Good luck! Poor little sweetie.
