You confuse extravagant language with the dogmas of the Church. First, note that the Virgin has always been regarded as an exaulted person, because she is, after all, the Mother of the Lord, not like Elizabeth or Hannah, the mother of a prophet. And if Jesus is divine but also a man, then her role in the hypostatic union is enormously important. As she is fully human, she is the guarantor of the humanity of the Lord. But as he is divine, her role is as a witness to the part that the Father and the Holy Spirit played in the incarnation. Many evangelicals today object to the title of Mother or God, which I grant you is misleading, and the Eastern Title “Theotokos, meaning God-bearer , is more accurate, for its implies that it is through her that God entered the world in the form of a human being. No wonder that the cult of Mary “took off,” in the 4th Century, after the Church repudiated the teachings of Arius. But long before this, the Church help up Mary in high honor, because she was, as I have said, the proof that Jesus was not a spiritual being but a man. Further, that she was EverVirgin because the birth of Jesus was unlike any other human birth. This was already being said in the 2nd Century, as a response to the Gnostics.
The extravagant language of devotional works, as Robby notes, is not to be put on the same level as the Catechism or doctrine. But there is a sound reason for the existence of such works, especially in light of what Lewis calls "the discarded image" - the medieval and Renaissance worldview.
That worldview was different from ours in some fundamental ways. One was the concept of courtly love -- the devotion to a woman, ordinarily a noble, well-born lady, as an ideal to be admired and served from afar or below. Not out of self-interest, not out of any sexual element, but because part of the duty of a 'parfit gentil knight' was to treat women - of high or low degree - with respect and honor. The Blessed Virgin, as the woman of highest degree, was due the greatest respect and honor, and the most warm-hearted and devoted service.
This gave rise to an entire school of poetry and echoed down literature to Shakespeare and beyond. You see faint echoes of this not only in the homage paid to royalty, and in the devotion of an old-fashioned sort of man to his mother, but also in the traditional courtship where a young man speaks to his beloved in terms both extravagant and courtly.
He isn't really going to 'climb the highest mountain and swim the raging seas' for his young lady, nor are her eyes really like stars or her voice like music, nor is she lovely as the dawn, nor a goddess, nor does he in plain cold fact worship the ground on which she walks. But he says all these things, as an imperfect expression of his love and devotion. Nobody claims that on account of these facially false and outlandish statements that he is a heathen or a heretic, nor that he has put his beloved before God.
Bearing in mind this, bearing in mind also that the Church is slow to change because she is very old, and that men like St. Louis de Montfort (author of possibly the most popular devotion to Mary) were schooled in the old traditions of courtly devotion, perhaps you can better understand some of these expressions.
Some might think that the cold wind that blew through Geneva and Edinburgh and swept away the warm-hearted and pure devotion of gentlemen to the ideal of a great lady was a bad thing, at least in that respect.
Though, again, I think y'all can believe what you want, the idea that Mary remained a virgin after the birth of Jesus plays into the Gnostic thought. After all, they did not believe that Jesus came in the flesh. They taught that the material world was evil. Therefore, to say Jesus passed through the birth canal without changing Mary physically would have played into the false beliefs of the Gnostics. But Jesus WAS in physical, human form, he WAS/IS God incarnate - in the flesh. To teach Mary remained a virgin would BE Gnostic teaching, NOT Christianity.
I fully believe that Mary was a virgin when she conceived Jesus. He is the Messiah and that miracle was foretold in Isaiah 7:14. I also honor her faith and courage as well as her faithfulness to Jesus. But, teachings such as her perpetual virginity, her being the Mother of God, her sinlessness and it being necessary for her to bear Christ, her bodily assumption into Heaven and her role as mediator and dispenser of all graces I will pass on. Not only are these teachings NOT Scriptural, they even contradict Scripture. This is just one more proof to me that the Catholic Church is NOT the "catholic" church.