This thread is for SinginBeauty,
I hope to give you some understanding why we affirm the belief that Mary is the Mother of God, or Theotokos.
The Council of Ephesus affirms this. The Council Fathers states,
The holy and great Synod therefore says, that the only begotten Son, born according to nature of God the Father, very God of very God, Light of Light, by whom the Father made all things, came down, and was incarnate, and was made man, suffered, and rose again the third day, and ascended into heaven. These words and these decrees we ought to follow, considering what is meant by the Word of God being incarnate and made man. For we do not say that the nature of the Word was changed and became flesh, or that it was converted into a whole man consisting of soul and body; but rather that the Word having personally united to himself flesh animated by a rational soul, did in an ineffable and inconceivable manner become man, and was called the Son of Man, not merely as willing or being pleased to be so called, neither on account of taking to himself a person, but because the two natures being brought together in a true union, there is of both one Christ and one Son; for the difference of the natures is not taken away by the union, but rather the divinity and the humanity make perfect for us the one Lord Jesus Christ by their ineffable and inexpressible union. So then he who had an existence before all ages and was born of the Father, is said to have been born according to the flesh of a woman, not as though his divine nature received its beginning of existence in the holy Virgin, for it needed not any second generation after that of the Father (for it would be absurd and foolish to say that he who existed before all ages, coeternal with the Father, needed any second beginning of existence), but since, for us and for our salvation, he personally united to himself an human body, and came forth of a woman, he is in this way said to be born after the flesh; for he was not first born a common man of the holy Virgin, and then the Word came down and entered into him, but the union being made in the womb itself, he is said to endure a birth after the flesh, ascribing to himself the birth of his own flesh. On this account we say that he suffered and rose again; not as if God the Word suffered in his own nature stripes, or the piercing of the nails, or any other wounds, for the Divine nature is incapable of suffering, inasmuch as it is incorporeal, but since that which had become his own body suffered in this way, he is also said to suffer for us; for he who is in himself incapable of suffering was in a suffering body. In the same manner also we conceive respecting his dying; for the Word of God is by nature immortal and incorruptible, and life and life-giving; since, however, his own body did, as Paul says, by the grace of God taste death for every man, he himself is said to have suffered death for us, not as if he had any experience of death in his own nature (for it would be madness to say or think this), but because, as I have just said, his flesh tasted death. In like manner his flesh being raised again, it is spoken of as his resurrection, not as if he had fallen into corruption (God forbid), but because his own body was raised again. …
((the complete version is in the link I provided)).
If you have any question, I think the Catholic Apologists will help you understand this more. This is not for SinginBeauty but for other Protestants who have diffculty with the title.
Thanks be to God.