There is the Virgin Mary: the Mother of Jesus, who we find in the Gospels. What happens is that She has several titles. The different names and the different images allude to the different circumstances or mysteries of her life, such as: the Annunciation, the Assumption, the Immaculate Conception, etc.
There are also names that refer to the places where She is venerated like Fatima, Portugal, or Lourdes, France. Her other popular titles are: Mary Help of Christians, Our Lady of Mount Carmel, Our Lady of Guadalupe and Our Lady of the Rosary.
Likewise, there are many names to refer to Jesus, which doesn't mean that there is more than one Jesus: Good Shepherd (John 10:11), Christ, the Son of God (Matthew 16:16), Lamb of God (John 1:29), King of Kings (Revelation 19:16 ), etc.
Therefore, we ought to refer to different titles of Our Lady, not to how many Virgin Marys there are. The Virgin Mary has appeared many times and in different ways, because She looks for a way to be understood by those who see and hear Her and adapts to the culture She appears in. For example, Our Lady of Guadalupe, who appeared in Mexico to the Indian, Saint Juan Diego, was dressed like a native princess of the Mexican people. In this way, She teaches us that, while She is the Mother of God she is also Our Mother. You do the same thing: you don't always wear the same clothes; depending on the occasion, you dress accordingly.
The Virgin Mary's titles are a pious Christian custom that manifest the maternal affection She has for people all over the world, but we have to learn their true meaning to avoid superstition and confusion.
-Response from Fr. José Javier, SHM