Maria is the vampire who created Jasper Hale and raised an army of newborn vampires. Maria found Jasper Whitlock during the Southern Vampire wars.
At this point, Jasper was a major in the Confederate Army, and Maria was looking for humans that she could transform into vampires to create a newborn army, using the idea pioneered by Benito.
After turning Jasper, she found that he was extremely useful to her, because he was able to control the emotions of other vampires around him, and make them work together.
With Jasper, Nettie and Lucy, she was able to take over many Mexican territories previously owned by other vampire clans. Jasper was very close to Maria, and Jasper thought of her as a god-like figure. In the movie version of Eclipse, Jasper and Maria are said to be romantically involved and they kissed. While Jasper believed what they had was love, Maria was simply using him as "her puppet." Jasper was often rewarded by Maria, especially for helping her defeat Nettie and Lucy when they rebelled.
One night, Maria ordered Jasper to "purge" the newborns, which meant for him to kill all of the newborns that showed no potential to remain in her coven. It made Jasper sick and depressed to do this, and so, Jasper later ran away with two other members of Maria's army, Peter and Charlotte, who he had let escape years before.
It is unknown what became of Maria, although in the Midnight Sun draft Edward mentions that she once sought the Cullens out when they were in Calgary, prompting them to move again; Jasper politely told her to keep her distance in the future. Jasper also asks Peter and Charlotte to tell Maria that he wishes her well, should they meet her again, so it can be assumed that Maria is still alive. It is unknown whether she is still creating newborn vampires.
In Eclipse, Maria is described as a tiny brunette with a soft and musical voice with a tendency to be sharp. In the movies, she has black hair and is of Mexican descent. Furthermore, while she is only mentioned in the book, she actually appears in the movie.
Catalina Sandino Moreno portrays Maria in the film Eclipse.
While helping fight, win and recruit more vampires in her coven, Jasper grew fond of Maria, while she only pretended to return the feelings. This was because, unlike Alice Cullen, who loved him for what he was, Maria found him useful in controlling and killing the newborn vampires of her army.