That makes sense ... Ive never heard of the D-R translation. But even if it is translated “she” the nearest antecedent is Eve ... Mary is nowhere even imagined in the context.
That was my beef.
The Douay-Rheims translation was the only "approved" translation for the Roman Catholics before the 1960's and Vatican II. Some "dyed-in-the-wool" Catholics still cling to it much like the KJV-only "Protestants" they like to ridicule.
I think the nearest antecedent is "her seed", rather than "her" and that is why I agree that it was speaking of Christ. I think it is also considered one of the first Messianic prophesies in the OT.