You also might tell her that at every Mass her grandmother attended she said a form of the sinner’s prayer as cited here:
Penitential Rite (From Wikipedia, the free encyclopedia)
In the Roman Catholic Church, the Penitential Rite is a part of the Introductory Rites of the Mass. The Penitential Rite is a time of reflection on ones sins and a prayer for God’s mercy…
The Rite
The Penitential Rite follows the entrance procession and the greeting. The priest’s opening comments generally transition directly into the Penitential Rite.
The available forms are:
Option A (Often called the Confiteor or Mea Culpa; the most popular form):
All: I confess to almighty God,
and to you, my brothers and sisters,
that I have sinned through my own fault,
in my thoughts and in my words,
in what I have done,
and in what I have failed to do;
and I ask blessed Mary, ever virgin,
all the angels and saints,
and you, my brothers and sisters,
to pray for me to the Lord, our God.
Option B (Infrequently used):
Priest: Lord, we have sinned against you: Lord, have mercy.
Congregation: Lord, have mercy.
Priest: Lord, show us your mercy and love.
Congregation: And grant us your salvation.
Option C (May be said by the deacon or priest):
Minister: (The priest prays a short, spontaneous invocation): Lord, have mercy.
Congregation: Lord, have mercy.
Minister: (Second invocation): Christ, have mercy.
Congregation: Christ, have mercy.
Minister: (Third invocation): Lord, have mercy.
Congregation: Lord, have mercy.
The Penitential Rite always concludes:
Priest: May almighty God have mercy on us, forgive us our sins, and bring us to everlasting life.
Congregation: Amen.
The Kyrie eleison follows the Penitential rite, unless Form C is used, because Form C incorporates the Kyrie. The Gloria follows the Kyrie, and the Introductory Rites conclude with the Collect.