Mater veritatis is not a title alien to Catholic mariology, but it is certainly underused. I found one example from an old prayerbook, and a musician named Jean Mouton includes it in a version of the chant Felix namque. The text, ruthlessly plundered from a Rutgers University musical performance program.(PDF warning!)
Felix namque es, sacra Virgo Maria,
et omni laude dignissima:
quia ex te ortus est sol justitiae,
Christus Deus noster.
Ave regina caelorum
Mater regis angelorum, Dominus tecum,
Mater pietatis, Dominus tecum,
Mater veritatis, Dominus tecum,
Mater charitatis Dominus tecum.
O Maria, flos virginum,
velut rosa vel lilium:
funde preces ad Dominum
pro salute fidelium.
O Maria, mater Dei:
nos recommenda, tuo filio.
Pulchra es et decora, filia Jerusalem.
Gloria tibi Domine,
qui natus est de virgine,
cum patre et Sancto Spiritu,
in sempiterna secula.
For you are happy, O holy Virgin Mary,
and most worthy of all praise:
since from you has risen the sun of justice,
Christ our God.
Hail, Queen of heaven,
Mother of the King of angels, the Lord be with you,
Mother of piety, the Lord be with you,
Mother of truth, the Lord be with you,
Mother of charity, the Lord be with you.
O Mary, virgin flower,
as the rose or lily:
pray to the Lord
for the salvation of the faithful.
O Mary, Mother of God:
Mother of piety,
Mother of charity,
Mother of truth,
commend us to your Son.
You are fair and beautiful, daughter of Jerusalem.
Glory be to you, Lord,
who is born of a virgin,
with the Father and the Holy Spirit