I don’t think she has any infectious problem, but stray chickens can possibly be carriers of a disease (respiratory or something like Mareks disease.) That is the reason many people quarantine for a minth, just to watch for any unusual symptoms. But that is up to you to quarantine or not. She may do fine with the other chickens once her wound has healed, but if she is put with them now, they may hurt her by pecking at the red wound. Many people use a wire dog crate or cage next to the other chickens to introduce them over a week or two. Put her food and water in there. The betadine followed by the flammagel is fine to use on the wound. Once it has healed and feathers are growing back, she should be good to add to the flock.