This is rather simplistic, but this came to me while praying the Rosary:
“…(and you yourself a sword will pierce) so that the thoughts of many hearts may be revealed.”
[Gospel of Jesus Christ according to St. Luke, 2:35]
I don’t know what is meant by “sword.”
We might think to take it literally to mean that she would die a death related to that of her Son, but that this must be so that she could be assumed into Heaven, wounded like her Son, for her mission as Advocate for poor sinners whose thoughts and prayers she hears.
We might think of it in another way. We often hear of her Immaculate Heart being pierced with thorns. This tells of her woundedness. And so, in a spiritual way, we might take “sword” to mean that she would know the wounds of sin in her heart, especially the sins of priests and bishops, those who are configured to her Son, closest to her in daily activity, and who should be blameless before God. And she will know who are faithful and blameless and who are not by their thoughts and deeds. This may be why she calls us to always pray for her priests and bishops. This must be a difficult burden.
Let us pray with Mother Mary for all priests and bishops, for their sanctity and holiness in daily activity.