What was the relationship between Esther and Mary?
The Catechism says that some holy women prepared for Mary’s mission. It names Esther. Esther 4:8; Luke 1:38
What the Bible says
Esther 4:8
He gave him also a copy of the edict which was hanging up in Susan, that he should shew it to the queen, and admonish her to go in to the king, and to entreat him for her people.
Luke 1:38
And Mary said: Behold the handmaid of the Lord; be it done to me according to thy word. And the angel departed from her.
Douay-Rheims Bible (Challoner revision), public domain.
What the Church teaches
The Catechism names Esther among the women who kept alive the hope of Israel. The purest figure among them is Mary.
Catechism 64 · Catechism of the Catholic Church
Did you know?
According to the Catholic Encyclopedia, the Fathers of the Church saw in Esther a figure of the Virgin Mary. Catholic Encyclopedia (1909), “Esther”