Bad translation, or intentional distortion?
Intentional distortion.
It’s one of the many ways they use to justify the claims they make about Mary and her supposed role as “co-redemtix” as their catechism claims she is.
When Jerome translated into Latin many errors where made. The Douay-Rheims is translated from that Latin (the Vulgate) and no attempt has been made by the Catholic Church to correct those errors. If they did much of their doctrine would need to change. So while it originally was translation error it has become intentional. It remains the dogma of the Catholic Church to this day.
From the declaration of the dogma of the Immaculate Conception in Pope Pius IX’s Apostolic Constitution, Ineffabilis Deus:
Hence, just as Christ, the Mediator between God and man, assumed human nature, blotted the handwriting of the decree that stood against us, and fastened it triumphantly to the cross, so the most holy Virgin, united with him by a most intimate and indissoluble bond, was, with him and through him, eternally at enmity with the evil serpent, and most completely triumphed over him, and thus crushed his head with her immaculate foot. [http://catholicbiblestudent.com/2013/02/mary-crush-serpents-head.html]