And it came about, as her soul was departing (for she died), that she named him Ben-oni; but his father called him Benjamin. Genesis 35:18 (NASB)
In verse 18, Rachel's death is tied to her "soul departing." The word "soul" here in Hebrew is נֶפֶשׁ (nefesh), which is first used in Genesis 1:20 where "living creatures" are first mentioned. It implies a kind of... essence of life or life-force. When the text says that her nefesh "was departing," it describes an active and ongoing process. But when the text says "for she died," the grammar requires a completed action.
In English, we might say "she was dying," but the phrase here in Genesis 35:18 puts the emphasis on life: "her life-force was leaving, and she died." The emphasis is the living.