We Disagree, Because of non-biblical evidence.Early Christian witness
The early Church Fathers recognised Mary as the Mother of God. Here are a few quotes from them:
"The Virgin Mary, being obedient to his word, received from an angel the glad tidings that she would bear God" (Iranaeus - Against Heresies, 5:19:1 [A.D. 189]).
"[T]o all generations they [the prophets] have pictured forth the grandest subjects for contemplation and for action. Thus, too, they preached of the advent of God in the flesh to the world, his advent by the spotless and God-bearing (theotokos) Mary in the way of birth and growth, and the manner of his life and conversation with men, and his manifestation by baptism, and the new birth that was to be to all men, and the regeneration by the laver [of baptism]" (Hippolytus - Discourse on the End of the World 1 [A.D. 217]).
"For Luke, in the inspired Gospel narratives, delivers a testimony not to Joseph only, but also to Mary the Mother of God, and gives this account with reference to the very family and house of David" (Gregory the Wonderworker Four Homilies 1; 262 AD).
"(Those engaged in the public transport service) came to the church of the most blessed Mother of God, and Ever-Virgin Mary, which, as we began to say, he had constructed in the western quarter, in a suburb, for a cemetery of the martyrs" (Peter of Alexandria The Genuine Acts of Peter of Alexandria; 305 AD).
"While the old man [Simeon] was thus exultant, and rejoicing with exceeding great and holy joy, that which had before been spoken of in a figure by the prophet Isaiah, the holy Mother of God now manifestly fulfilled" (Methodius Oration on Simeon and Anna 7; 305 AD).
"We acknowledge the resurrection of the dead, of which Jesus Christ our Lord became the firstling; he bore a body not in appearance but in truth derived from Mary the Mother of God" (Alexander of Alexandria Letter to All Non-Egyptian Bishops 12; 324 AD).
"The Father bears witness from heaven to his Son. The Holy Spirit bears witness, coming down bodily in the form of a dove. The Archangel Gabriel bears witness, bringing the good tidings to Mary. The Virgin Mother of God bears witness" (Cyril of Jerusalem Catechetical Lectures 10:19; 350 AD).
"Though still a virgin she carried a child in her womb, and the handmaid and work of his wisdom became the Mother of God" (Ephraim the Syrian Songs of Praise 1:20; 351 AD).
"The Word begotten of the Father from on high, inexpressibly, inexplicably, incomprehensibly, and eternally, is he that is born in time here below of the Virgin Mary, the Mother of God" (Athanasius The Incarnation of the Word of God 8; 365 AD).
"Being perfect at the side of the Father and incarnate among us, not in appearance but in truth, he [the Son] reshaped man to perfection in himself from Mary the Mother of God through the Holy Spirit" (Epiphanius of Salamis The Man Well-Anchored 75; 374 AD).
"The first thing which kindles ardor in learning is the greatness of the teacher. What is greater than the Mother of God? What more glorious than she whom Glory Itself chose?" (Ambrose of Milan The Virgins 2:2[7]; 377 AD).
This Virgin became a Mother while preserving her virginity;
And though still a Virgin she carried a Child in her womb;
And the handmaid and work of His Wisdom
became the Mother of God
(St Ephraim, Songs of Praise, 1, 20; c. 381 AD)
"If anyone does not agree that Holy Mary is Mother of God, he is at odds with the Godhead" (Gregory of Nazianz Letter to Cledonius the Priest 101; 382 AD).
And don't tell God's revelation is in Scripture alone. That is not Biblical and a heresy.
Walter And Debbie