I have a chicken who was pecked SO badly, and I rehabbed her in isolation (put her in a dog crate that belongs to my pittie) and tended to her wound. At first, I flushed any broken skin with Betadine (the spray is super handy) and then cleaned it numerous times a day with either neosporin (make sure it doesn't have the painkiller in it) or Vetricyn spray.
Your chicken doesn't look too awful, but I would separate her from the others until she recovers. Chickens sense weakness and injury and will just keep picking on her otherwise.
Once she's good to go, slowly reintegrate her to the flock. At first, supervise their interactions to be sure they don't go back to their old ways. If her wound looks reddish or in anyway like an injury, used Bluekote or Pick No More to deter the others.
Do you let your chickens free range or are they in an enclosure all day. They could be behaving like this due to confinement or boredom.