The Apostolic constitution of Pope Pius XII states: “We pronounce, declare, and define it to be a divinely revealed dogma: that the Immaculate Mother of God, the ever-Virgin Mary, having completed the course of her earthly life, was assumed body and soul into heavenly glory.” — Pope Pius XII, Munificentissimus Deus, 1950
The question of whether Mary died is significant especially in the context of the Assumption. The story of the Dormition of Mary from the Eastern Orthodox Church, which is based on Tradition, way before the split between the East and the West in around 1054 AD, gives us a more definitive picture of the Assumption of Mary:
At the time of her death, the Apostles who were preaching throughout the world returned to Jerusalem to see the Theotokos (i.e., Mother of God). Except for Thomas, all of them including the Apostle Paul were gathered together at her bedside.
At the moment of her death, Jesus Christ Himself descended and carried her soul into heaven. Following her repose, the body of the Theotokos was taken in procession and laid in a tomb in Gethsemane. When Thomas arrived three days later, he desired to see her body; the Apostles went and found the tomb to be empty. The bodily assumption of the Theotokos was confirmed by the message of an angel and by her appearance to the Apostles. The apparition confirmed that Christ had taken her body to heaven after three days to be reunited with her soul.
It makes perfect sense that Mary died because it was her participation in the Death of her Son. During the funeral Mass, one of the prayers for the soul of the deceased says: “Remember your servant (N.) whom you have called from this world to yourself. Grant that he/she who was united with your Son in a death like His, may be one with Him in His Resurrection…” One of the lessons of the Assumption is about Death and Resurrection. The faithful need not be afraid of death as the end of everything and something to avoid at all costs, but a participation in the death of our Lord Jesus Christ and a step towards our participation in His Resurrection as well.
At the Assumption, Mary’s body was reunited with her soul. After Jesus’ first coming, Mary had the singular privilege of being the first to participate in her Son’s Resurrection. All the other saints after her will have to wait until the Resurrection of the Dead after the Final Judgment for their bodies to reunite with their souls in heaven.
Mary is our model in life and in death. Her unparalleled closeness with Jesus throughout her earthly life, in His conception, in His birth, childhood, adult life, His ministry throughout Galilee, His entry into Jerusalem, His suffering, death and burial, His Resurrection and Ascension.
There is no greater intercessor to Jesus than Mary. Mary will bring us closer to Jesus if we ask her.