Translation:Kati is fighting among the police officers and reporters.
no she is not fighting them. it is either as you said:
police officers and reporters are just hanging around and watching while Kati fights amongst them
or they are fighting together, on the same "side"
fighting them could be using -val/-vel (with):
- "Kati a rendőrökkel és a riporterekkel harcol"
or even more clearly, with ellen (against):
- "Kati a rendőrök és a riporterek ellen harcol"