Song of Songs is a poem about a man who loves a woman, to the exclusion of all other woman. She is elevated above all other women, and adorned as such.
The story isn't about the rejection of other women in the poem. It's about a special relationship.
In a way, the story of Noah and the Flood in Genesis 6 and 7 is the same story as the Song of Songs.
Here is the difference:
Perhaps neither of these "other" groups are meant to point to people.
The "other women" in Song of Songs are the heavenly hosts that cheer the union.
The "people not on the boat" are the demonic forces that God will destroy because they desire to harm His bride.