In order to understand where Cain's wife came from (She was not a daughter, nor granddaughter; or even a relative of Adam and Eve; or Abel nor Seth, etc.), we need to, first, know that: 1) The Adam of Genesis 2:8-4:1 was only the main Adam; and not the only [a]dam that GOD Created, which are mentioned and/or alluded to in Genesis 1:26-2:7; It is in Genesis 1:28-30, 2:7, that we are given the details of GOD’s Creation of “manâ€-kind, and not The Adam of Genesis 2:8-4:1. 2) The Adam of Genesis 2:8-4:1 did not name all the animals of Planet Earth; Adam didn’t name all the animals on “the earthâ€; but only the ones that GOD “brought†to him (and note the words “the fieldâ€, as opposed to “the earth†that is used in Genesis 1:1-2:6). Now, unless GOD brought “the fish of the sea†to Adam to be named, he didn’t name them either. 3) The Adam of Genesis 2:8-4:1 was not one of the ones that GOD addresses in Genesis 1:28-30. There is yet to be an Eve, although GOD, on “the sixth dayâ€, has already “created†them “male and female†and “GOD†has already “blessed them, and. . .said unto them, Be fruitful, and multiply, and replenish the earth, and subdue it: and have dominion over the fish of the sea, and over the fowl of the air, and over every living thing that moveth upon the earth.â€, and no further mentioning of this blessing is made anywhere in Chapter two. 4) Cain’s future wife was already a resident of “the land of Nodâ€, before he arrived there. We’re told in Genesis 4:6 that, “And Cain went out from the presence of THE LORD, and dwelt in the land of Nod, on the east of Eden.â€; in order for us to know that it was “the land of Nodâ€, it had to have been already named, because it was already occupied by humans. . .otherwise, telling us that it was “the land of Nod†would make absolutely no sense; it would have been meaningless. . .especially since “Nod†is never again mentioned in Scripture. 5) In Genesis 6, prior to “The Floodâ€, we’re [re]introduced to some beings referred to as “the sons of GODâ€, and others who are referred to as “the daughters of menâ€. Cain’s wife was one of the off-springs of one of “the sons of GODâ€; These same “sons of GOD†are those Created by GOD and spoken to in Genesis 1:26-30 (and also about in Genesis 2:7). And here we have the identity of “Cain’s Wifeâ€. Questions are welcomed.
Well, at least you're being creative in your interpretation. That's a start. My own pet theory is much simpler. It seems to me that the personalities mentioned prior to the flood, even prior to Abraham, are a literary convention intended to condense the history of tribes and kingdoms. Treating them as if they were people who "begat" other people was a way of expressing how one culture fades and gives rise to another. The Cain and Abel episode strikes me as an allegory of war. Otherwise, it makes no sense. The war was between shepherds and farmers, who come into natural conflict. Actually wrote a long poem about it, called, "The Shepherd's Lie." The Bible was written by a shepherd culture, so naturally the story begins by justifying the heritage of the author. I wouldn't take it too literally. That's a major misunderstanding.
Consider this, and let me know what you think: The “man†created and/or commanded in Genesis 1:26-28 is “manâ€-kind (called “the sons of GOD†in Genesis 6), and not the Adam we’re introduced to beginning at Genesis 2:8; They are created, along with Adam, to be replacements for Lucifer (now Satan/the devil) and all the angels that decided to follow him in his attempted coup d’etat against GOD that is described in, among other places in Scripture, Isaiah 14:12-19, Ezekiel 28:12-19, Jude 1:6, and Luke 10:18. In Genesis 2:7, Adam is Created for the purpose of becoming the One “to dress it and keep it (The Garden of Eden)†and to share, “freelyâ€, with all the other “sons of GODâ€, the fruit from “the Tree of Lifeâ€; The intent was for him to, first eat of it himself, and then to share it with his counterparts (“the sons of GODâ€); The Garden of Eden in Genesis 2-3 is the replacement Eden (to which had been Lucifer’s base of Operations), mentioned in Ezekiel 28:13 (Is it any wonder Satan, in the form of “the serpentâ€, invaded and attacked Adam and Eve there?). Because Adam sinned in much the same way, in the Garden, that Lucifer had done, He got a similar (but not the same exact) punishment, Expulsion, but with a twist, HOPE of REDEMPTION by GOD, in THE PERSON of “her SEEDâ€.