Because she was Born without the stain of Original Sin.
Virgin Mary?
She is the only woman who gave birth while still a virgin
The Blessed Virgin Mary
The virgin Mary was chaste because the Bible calls her a virgin. She was obviously a young woman who God trusted and respected enough to choose her to carry and care for His son Jesus
Mary is the only woman who had a child while still a virgin. She never had intercourse with any man not even Joseph.
She was good enough to be the mother of God.
No. Mary wouldn't exist if it wasn't for God Almighty. God simply chose Mary because she was a virgin woman from the tribe of David [which fulfilled the prophecies] and Joseph because he was a just man of the tribe of David.
No, Mohammad is not in the lineage of the Virgin Mary. The Virgin Mary is a descendent of King David.
The galilean woman who was sinless and full of grace is also known as The Virgin Mary or Mary the Mother of God. She was also called Mariam.
No, Virgin Mary is not single.
She is the Mother Of God and Our Mother too.
Personally, no, I have not seen the Virgin Mary.