She has the mindset of a peace-loving and calm woman, often thinking that fighting, even if it is for a good cause, can result in dangerous consequences and the very sight of danger (especially if it involves any of her loved ones) leads her to suffer strong attacks of hyperventilation. This was the main reason that Maria left Rodolfo and Miracle City, until she moved back several years later.
She cares a lot about Manny and worries about him with his El Tigre powers. While Rodolfo still shows his love for her, she maintains only a friendly relationship with him. However, she may still love for him, as she only left him because she could no longer bear witness to him injuring himself while he was a hero. Her occupation in most of the series is the librarian at Manny's school, where it is shown that she loves books.
While in college, Maria was a superhero called Plata Peligrosa but she went into retirement, because the glove (the source of her powers) was starting to take control of her, driving her crazy and making her very destructive. At some point after these events, she marries Rodolfo Rivera (White Pantera) and together, they have a son they would name Manny.
At this point, she accepted Rodolfo being White Pantera, al least until she witnessed a supervillain attacking Miracle City one day. When she saw Rodolfo getting hurt, she entered a state of hyperventilation. This continued on for some time until she couldn't take it anymore. She decided to leave her family behind.
After separating from Rodolfo, she gained success as a mariachi singer, recording numerous music discs and giving concerts around the world (many of which her son and the rest of their family attended). After years of a successful career in the field of music, she returns to Miracle City to be at the side of Manny.
Maria assumes the role of the Leone School's librarian, and seemingly always has a book on hand to back up a fact. She continues to be a functioning part of the Rivera family despite the separation between her and Rodolfo, such as attending a school parent-principal conference with Rodolfo in The Late Manny Rivera, coming over to the Rivera household for dinner often, even as far as attending a family dinner for Grandpapi's 'special announcement' in Bride of Puma Loco.
At one point, she was responsible for helping villains redeem themselves in Miracle City Worker. Though two villains were just using her to pull off a crime, one of them El Cucharon helped her son in defeating them and decided to make new life because of Maria who was overjoyed at least one chose to become good.
According to Jorge Gutierrez, Maria and Rodolfo eventually get back together once Rodolfo finally retired from being a superhero. This may possibly be that once Rodolfo actually retired from superhero, Maria was able to return to him.
The gallery for Maria Rivera can be found here.