The first reading (Song of Songs 3: 1-4) is one of the few times that this book of love poetry from the Hebrew Scriptures appears in the readings at Mass. It captures the intensity of Mary Magdalene's love for Jesus: "I sought him whom my heart loves--I sought him but I did not find him." Thus she returned to the empty tomb on Easter Sunday morning looking for the body of Jesus. But he had risen and, after showing himself to her, he sent her to the apostles to tell them the news of his resurrection. Thus she is known to this day as "the Apostle to the Apostles."
Here's something Pope St. John Paul II said about her on this day during the Jubilee Year 2000:
We are celebrating the feast of St Mary Magdalene and the liturgy today is marked by a kind of movement, a "race" of the heart and the spirit, motivated by the love of Christ.
Mary Magdalene followed to Calvary the One who had healed her. She was present at Jesus' crucifixion, death and burial. Together with Mary Most Holy and the beloved disciple, she witnessed his last breath and the silent testimony of his pierced side: she understood that her salvation lay in that death, in that sacrifice. And the Risen One, as today's Gospel recounts, wished to manifest his glorious body first to the one who had wept profusely at his death. To her he "first entrusted ... the joyful news of his resurrection" (Opening Prayer), as if to remind us that the shining glory of his resurrection is revealed precisely to those who look with faith and love on the mystery of the Lord's passion and death.