An infection causes an abscess, usually bacterial but I believe some can be fungal in nature.
She needs to continue to keep it clean. She can also put on topical antibiotic ointment (one without painkiller additive) like neospirin or bacitracin. I'd suggest a dose of oral or IM antibiotics to help neutralize the infection, too. Someone more knowledgeable on poultry medicines and doses will likely chime in on what and how much.