Answer:
She is the patron saint of Mexico. The symbolism of the Virgin Mary of Guadalupe can be traced back to Aztec times, when Coatlicue, the divinity of life and death was revered. Spanish conquistadors saw this, then mixed both Aztec and Catholic beliefs to better control the populace. This is known as religious syncretism.
Usually, on December 12th several pilgrims from around the country reach the Guadalupe Basilica in Mexico City, and attend a mass given by Mexico's archbishop. After such event, some people display fireworks outside of the church.