I don't know that a vet would prescribe antibiotics without examining her. Do you have access to an avian vet? Also, what temperature is the bathroom? Can she get away from the heat if she needs to?
I am not an expert on antibiotics. I would have to look it up. If she were mine, I would try...
I believe that is a normal temperature for a chicken. You may have to tube feed her to sustain her. @casportpony is the authority on that, and may be able to help with antibiotics, as well. I would not treat with antibiotics if I did not know there was an infection, but that might be a good...
She looks like she is healing well. I would consider the possibility that she has an infection, however. Did you check that she doesn't have wounds elsewhere besides the ones on her back?