Looks like a pretty classic case of feather picking, Thunder Chicken. You can see where some of the others have had feathers pulled as well. If you saw her poking at the area, she was most likely trying to preen or clean up the area. The other hens are most likely the culprits. This is usually either from boredom, overcrowding, or even a protein deficiency. Do you let them free-range at all or very often? I'm guessing you don't have them overcrowded, so my first thought is boredom. I had feather-picking pretty badly one year and ruled out boredom and overcrowding (we had expanded the run that year from about 20x45 to 50x100), so I switched my girls to a higher protein feed. I still see some picking going on, but much less.
What I do if I see feather-picking that bad is I cover the area with Blu-Kote, which disguises the wound and puts the others off from pecking at it. If that doesn't help, you'll have to keep her separate until she heals over. Antibiotic cream wouldn't hurt assuming it does NOT contain any pain reliever that ends in '-caine' (lidocaine, benzocaine, etc.), but unless she is separate, the other girls might see the ointment and poke at her more.