I reintroduced my injured hen before the feathers grew back. Just coat the area with BluKote & they left it alone. Although I didn't reintroduce at night, & she got attacked by the other girls on her head.
She had been top chick, but the absence made her lose that place. I don't know if reintroduction at night would've prevented that. However, like you, we're in the cold snowy area of the country, so I didn't want to leave her out at night before she'd been acclimatized, so I let her out to free-range during the day & brought her back in at night when it got cold. She's now been with the other girls about 1 1/2 weeks, and has been accepted back, just lower on the ladder.
You're girl looks much better! I do hope you can figure out what's doing the damage. You probably want to make sure it is fully scabbed before releasing her because she will give herself a dustbath in the first day or two, and you don't want her getting that dirt into the wound.

You're girl looks much better! I do hope you can figure out what's doing the damage. You probably want to make sure it is fully scabbed before releasing her because she will give herself a dustbath in the first day or two, and you don't want her getting that dirt into the wound.