If, is an ant bite...Fire Ants, are the ones you should be concerned about. Fire ants inject a venom that is very painful, and can cause infection to develop.
Treatment would be to wash the bite area, then, apply some ice to the site to relieve pain.
If the hen is limping, and it is evident that infection is starting, treat similar to bumble foot, apply Neosporin ointment (without pain reliever), place a small piece of gauze over the bite, wrap with self stick gauze or vet wrap. Check every couple days or more, if you like. It should heal up fine, as long as she is eating and drinking, and not in shock from the venom.
Fire ants can kill a chicken. It all depends on how many ants attack, the size of the chicken and the general health of the chicken.
Fire ants inflict a severely painful bite, I know I was attacked about 10 years ago. I'll never forget it! I didn't even know we had fire ants here in California, but, they are spreading everywhere.
God Bless