"La ragazza era arrivata nell'appartamento circa un anno fa."
My translation (rejected): The girl had come to the apartment about a year ago. The "correct" translation is not natural English - it would sort of stylistic, anyway. Being an English speaker, I don't know if this is the most natural way to express this idea in Italian (as opposed to using venire).
It's weird either way. It sounds like someone came one year ago and never left the apartment again.