Mary, the New Eve
The question
Where does the Bible ever call Mary a "new Eve"?
Scripture · Genesis 3:15
I will put enmity between you and the woman, and between your seed and her seed; he shall bruise your head, and you shall bruise his heel.
A short answer
You won't find the phrase "new Eve" printed in Scripture — so the objection that it's a later invention seems fair. But the pattern is woven right into the text, and the earliest Christians spotted it immediately. The whole Bible is built on echoes: Adam and the new Adam, the old covenant and the new. Where there's a new Adam, the logic of Scripture leads us to look for a new Eve.
Paul calls Jesus the "last Adam" (1 Corinthians 15:45) — the one who undoes what the first man broke. Eve said no to God and brought death; Mary said "let it be to me according to your word" (Luke 1:38) and brought us the Author of life. Jesus even addresses His mother as "Woman" at Cana and from the cross (John 2:4; 19:26), the exact word God used for Eve in Genesis. That's not an accident. And Genesis 3:15 promises a woman whose seed will crush the serpent's head — a verse the Church reads as fulfilled in Mary and her Son (CCC 410-411, 494).
St. Irenaeus put it best in the second century: "the knot of Eve's disobedience was loosed by the obedience of Mary." Mary as the new Eve isn't a doctrine bolted on later — it's the Church reading Scripture the way Scripture asks to be read, by its own internal echoes.