Sometimes we are asked questions about intercessory prayer and why one might feel called in their heart to ask Sr. Marie to be the sole intercessor for a particular petition or favor. The Catechism of the Catholic Church addresses Prayer of Petition, Prayer of Intercession,The Intercession of the Saints, and the Communion of Saints.
CCC #2629 Prayer of Petition
CCC # 2634-2635 Prayer of IntercessionThe vocabulary of supplication in the New Testament is rich in shades of meaning: ask, beseech, plead, invoke, entreat, cry out, even "struggle in prayer."102 Its most usual form, because the most spontaneous, is petition: by prayer of petition we express awareness of our relationship with God. We are creatures who are not our own beginning, not the masters of adversity, not our own last end. We are sinners who as Christians know that we have turned away from our Father. Our petition is already a turning back to him.
Intercession is a prayer of petition which leads us to pray as Jesus did. He is the one intercessor with the Father on behalf of all men, especially sinners.112 He is "able for all time to save those who draw near to God through him, since he always lives to make intercession for them."113 The Holy Spirit "himself intercedes for us . . . and intercedes for the saints according to the will of God."114
CCC # 956 The Intercession of the Saints.Since Abraham, intercession—asking on behalf of another—has been characteristic of a heart attuned to God's mercy. In the age of the Church, Christian intercession participates in Christ's, as an expression of the communion of saints. In intercession, he who prays looks "not only to his own interests, but also to the interests of others," even to the point of praying for those who do him harm.115
The intercession of the saints. "Being more closely united to Christ, those who dwell in heaven fix the whole Church more firmly in holiness. . . . [T]hey do not cease to intercede with the Father for us, as they proffer the merits which they acquired on earth through the one mediator between God and men, Christ Jesus. . . . So by their fraternal concern is our weakness greatly helped."495Finally, CCC #962 helps us understand the Communion of Saints.
"We believe in the communion of all the faithful of Christ, those who are pilgrims on earth, the dead who are being purified, and the blessed in heaven, all together forming one Church; and we believe that in this communion, the merciful love of God and his saints is always [attentive] to our prayers" (Paul VI, CPG § 30).
It is in the context of these understandings that we learn how we can pray to God through the intercession of a Servant of God, a Blessed, or a Saint. As Servant of God, Sr. Marie de Mandat-Grancey is a special friend of God to choose. As the Church discerns the Cause for the Beatification of Sr. Marie, She looks closely at the testimonies of those who attribute heavenly favors to Sr. Marie's intercession. In order for any heavenly favor to be attributed to Sr. Marie's intercession, she must be the sole intercessor offering the petition to God.
All prayers are always offered to the Father through Our Savior Jesus Christ and His Blessed Mother Mary. In the case of prayers being offered in petition to God ( as always through Our Savior Jesus Christ and His Blessed Mother Mary) through the intercession of a Servant of God, or Blessed, or Saint, God can and does show His favor and blessings on the efficacy of the prayers of that particular intercessor. For example, if we offer a prayer of petition through the sole intercession of Servant of God, Sr. Marie, and God answers that prayer by granting a particular favor according to His perfect will, we and the Church may then know for sure that the favor was indeed granted through the intercessory prayer of Sr. Marie alone and can attribute the favor to her intercession. This becomes important in the process of Beatification and Canonization.
Even if we have asked other Saints in the past, we can begin anew a prayer petition through the intercession of Sr. Marie and state so in our prayers; from this point on, during this specific time of prayer ~ perhaps nine days, or nine hours, or from now until a certain date of some special significance~ Sr. Marie alone is the one I choose to intercede to God on my behalf with this petition. Perhaps we can write this down as a matter of record and keep it in a special place.
Then we can write our testimony as a way of thanking God and acknowledging Sr. Marie's intercessory role. As testimonies are gathered from all over the world from those who attribute answered prayers to the intercession of Servant of God, Sr. Marie de Mandat-Grancey, the case for her sanctity grows and we draw closer and closer in all hope to the glorious day of her Beatification.