Welcome to BYC
Looks like she's cut it somehow, maybe on fencing. I've seen this with birds that fence fight.
The injury is at least a few days old looks like to me. Clean well, I would use Chlorhexidine. Apply a very small amount of triple antibiotic ointment to the wound, then wrap with vet wrap. Let her be with her flock, but it's best for the wrappings to stay dry.
Clean and apply ointment daily. The "growth" is a piece of skin, it may dry up and fall off. If it gets "mushy" with the wrapping, then eliminate the triple antibiotic ointment and just swab with Chlorhexidine daily. Hopefully it will dry up and fall off on it's own.
