I agree with VGisondi in that the "I will put enmity between you and the woman" doesn't refer to giving women a fear of "snakes and creepy crawlies", but instead shows God putting a curse between mankind and the devil.
However, you said "You were right in saying that the woman God promised is Mary", but I don't understand, there is no promised woman? There is absolutely no mention of this woman is a 'future' woman, rather than Eve herself.
Also, nowhere in scripture will you find Mary, mother of Jesus being sinless, but as Luke 11:28 would indicate, she was in no way special other than the fact that Jesus was her son.
Much like the entirety of the bible shows us, (for example, Titus 3:4-7) the good things which God does for us are not because of our piety or righteousness, but rather because of His own mercy and generosity.
the catholic church puts unbiblical emphasis on Mary, for if she was sinless, that completely defies Jesus' purpose in living the perfect life and dying in our place.
The fact that God says that there is enmity between Satan and the woman (whom I would suggest is more directly Eve, not Mary) is the disparity between the devil and us, in that he would have us all damned.