After studying a little I think the serpents seed could be in all of us. The natural born sinner, the old us. And the women's seed is the christ in us.
Every human birthed into this world is spiritually contaminated with the seed of Satan. Rom 5:18 Therefore as by the offense of one judgment came upon all men to condemnation;
All natural human beings are incompatible with God. Joh 3:3 Jesus answered and said unto him, Verily, verily, I say unto thee, Except a man be born again, he cannot see the kingdom of God.
God sowed His seed (word seed): Gen 2:17 "But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die."
Satan sowed his seed (word seed): Gen 3:4 "And the serpent said unto the woman, Ye shall not surely die:"
The spirit beings of type man (Adam) received the seed of Satan and rejected the seed of God. They were spiritually birthed from Satan.
How do we know the Word is the seed? Mar 4:14 The sower soweth the word.
Satan is the legal owner of the natural man. 2Co 4:3 But if our gospel be hid, it is hid to them that are lost: 2Co 4:4 In whom the god of this world hath blinded the minds of them which believe not,
Good News.
God brought new Seed "her seed". Joh 1:1 In the beginning was the Word, and the Word was with God, and the Word was God. Joh 1:14 And the Word was made flesh, and dwelt among us, (and we beheld his glory, the glory as of the only begotten of the Father,) full of grace and truth.
Jesus told us that he brought new Seed. Joh 17:8 For I have given unto them the words which thou gavest me; and they have received them, and have known surely that I came out from thee, and they have believed that thou didst send me.
Every human can now escape from captivity through a new birth. 1Pe 1:23 Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth forever.