Hunak means "there" in the since of "at that place." You're thinking of the existential "there" in English, which expresses something that exists. There is no existential "there" in Arabic. We translate it many different ways. In this case, we use "fii" because it exists IN a specific place, the background. The existential "there" is implied. If we added "hunak" it would be more like, "There (in that place), in the background, is a rich woman" instead of "There is (exists) a rich woman in the background."
It's a subtle but important distinction.