I agree with this. I had a hen with a similar injury from a hawk attack last winter. I took a tough love approach and simply sprayed the area with bluekote. The area was smaller than yours, but a deep gouge. I brought mine inside by the heat because she was clearly in shock. That lasted one day before she was ready to go back out. She is bottom of the pecking order and was then picked on by the other hens, but she was quick and rebounded well.You'd be better off using a 50/50 betadine water mixture flushing the wound, do your best to avoid her eyes. Then pack the effected area with neosporin or triple antibiotic ointment. Continue to pack with antibiotic ointment until healed.
Keep her caged and provide her feed and water.
I would have done things differently knowing what I do now. I would have taken a more gentle approach as dawg mentions above and continued to keep her in a cage in the coop to protect her as she heals. If you can avoid infection, they bounce back well!