One other thing...
Throughout the entire passage, the woman serves as a representative for all women. The consequences of her decision - pain in childbirth, being ruled over by her husband - were extended to all women. Contextually, this same representative position of Eve should be accounted for in the entire passage. The woman referred to in verse 15 is the same woman as in the rest of the passage, serving in the same representative capacity.
Ergo, the woman must be Eve, not Mary.
How can this be if "her Seed" clearly does not refer to Cain or her other children?