This is a nasty wound. I would put Cheeru in the sink or tub and gently flush this wound with cool water until it is clean and all the discharge is removed. Then keep her inside in a small clean room with fresh bedding, food, water and litter. It looks like you may have put iodine solution on it as a disinfectant in the picture, which is fine. She will lick and clean this area so I don't like to apply ointment on it. You can take some hydrogen peroxide on a cloth and clean the area daily if needed. Draining watery, bloody fluid from the area is normal. Give her wet food with added water to make sure she doesn't become dehydrated. Luckily cats usually heal well when the wound is open and draining like this one. Expect this to take a few weeks to heal. Thanks for using Petco Pet Education Center, formerly Petcoach to help you care for Cheeru.