Oh my gosh is that a hens vent? That looks really bad. What happened?
I suggest cleaning it out immediately and putting disinfectant on it ASAP. poor girl. I hope everything turns out alright!
Do you know what this is? Just based on the picture I would first give a warm bath with some epsom salt and spray with Vetericyn Wound & Infection care spray three times a day. Give her Oregano tea. I use half a cup of oregano to make a gallon of the tea and leave it out free choice along with vinegar water - 1 tablespoon of apple cider vinegar with the “mother” to each gallon of their drinking water. You should also separate her if you can.
