Sister Faustina has succeeded in bringing the Trisagion Hymn back into the Catholic Church. However, that hymn is not included in the Mass where it should be.
The Trisagion Hymn: Holy God, Holy Mighty, Holy Immortal, have mercy on us. (3 times)
The Trisagion Hymn was originally in the original Mass of Pope St. Gregory. It was also in his PreSanctified Vespers Service that the Orthodox Christians use during Great Lent. The Catholics today do not even have a remnant of this beautiful Lenten Service on Good Friday, but if one compares the Good Friday Service prior to Vatican II to that used now, one will notice that the Trisagion Hymn is in that earlier service but not in the recent Catholic Good Friday Service, which has been really gutted, and is not recognizable.
All these liturgical changes in Catholicism have really been a shame.
If one were to compare the Tridentine Latin Mass (which is a modified Gregorian Mass), one would see some similarity with the Eastern Divine Liturgy, but as the centuries have passed, especially the 8th century, many Byzantine hymns and most of the Kyrie Eleison(s) were removed.