Maggie is part of a large Mexican-American family with branches in two states. Her father, Nacho Chascarillo, comes from a Texas family with connections in the pro wrestling world. Nacho is a womanizer; his own sister, Vicki Glori, says that he is the kind of man who should never get married. Maggie's mother, Quina, is a vague, apathetic woman who later suffers from some sort of low-grade mental illness. Maggie has four brothers (Calvin, Manuel, Angel, and Ruben), but she is closest to her kid sister, Esther.
Nacho and Quina divorce when Maggie is still a young child, in large part because Maggie discovers that Nacho is having an affair with a younger woman. Maggie accidentally reveals this knowledge to her mother, and her role in her parents' divorce gives Maggie a burden of guilt that she struggles with for the rest of her life.
Maggie's brother Calvin has a particularly tragic history. Calvin is sexually molested by an older boy at the same time that the Chascarillos' marriage falls apart. Calvin kills the other boy in a fit of rage, and thereafter his life is a story of sexual misadventures, collisions with the law, and personal failure. Maggie's parents keep much of the truth about Calvin from Maggie, and she rarely sees her oldest brother. Maggie is also unaware that Calvin has dogged her footsteps for many years, making sure that she is 'safe' from unwanted men and other dangers.
After her parents split, Maggie winds up living with Vicki Glori. Vicki is a professional wrestling champion, a tough, demanding woman with no experience of child rearing, and her relationship with Maggie is a difficult one. Maggie seems to have relatively little contact with her parents or siblings after the divorce and she suffers from unhappiness. Fortunately, Maggie has an understanding best friend, Letty Chavez, who introduces Maggie to punk music. Maggie has a natural gift for fixing things, and she soon becomes an apprentice mechanic.
Letty dies in a car crash while she is still young. Maggie's former babysitter, Izzy Ortiz, takes pity on her and tries to fill the void left by Letty's death by introducing Maggie to Hopey Glass. The sweet, shy Maggie and the rebellious Hopey soon become fast friends, much to the displeasure of Vicki Glori and Terry Downe, Hopey's lesbian girlfriend. Hopey and Maggie fall in love, beginning an on-off affair that will last for many years.
Despite her love for Hopey, Maggie is not completely lesbian; she is constantly falling for handsome men, often with unhappy results. Maggie becomes a "prosolar mechanic," specializing in robot and rocketship repair. This career leads her into a number of fantastic adventures in exotic countries, in the course of which she experiences a powerful but unrequited love for Rand Race, a handsome prosolar mechanic who has also had an affair with Maggie's friend Penny Century. During this period of her life, Maggie also becomes friends with Rena Titanon, a charismatic wrestling champion who has a second identity as a freedom fighter in third-world countries. Rena is also an old wrestling rival of Vicki Glori's, and Maggie's friendship with Rena puts even more strain on her relationship with Vicki.
Maggie's self-confidence is severely shaken by her romantic failure with Rand Race, so she gives up her mechanic career and returns to Hoppers to be with Hopey (who has evidently been sleeping with Terry again whenever Maggie is out of town).
Maggie eats too much, gains weight, works in dead-end jobs, and lives with Hopey for some time, but then Hopey departs on tour with Terry's band, La Llorona. After Hopey's departure Maggie nearly falls for her old childhood friend, Izzy's kid brother Speedy Ortiz. Everything ends tragically when Speedy's affair with Esther provokes a gang war; rejected by a confused Maggie, Speedy kills himself.
Maggie falls out with Vicki Glori and becomes involved with Ray Dominguez, another old acquaintance who has long had a secret affection for Maggie. Their affair lasts for about two years, but ends when Maggie goes to the East Coast to reunite with Hopey. This reunion is brief, however, and a rootless Maggie journeys to Texas where she again becomes involved in her family's affairs. Maggie also meets El Diablo Blanco, a Mexican wrestling star who turns out to be Rena Titanon's brother, and Maggie and El Diablo help Rena defeat a gang of kidnappers.
Hopey and Maggie find one another again and they settle in Los Angeles, but they do not remain under the same roof for very long. For a while, Maggie works as a personal assistant to Norma Luna, an out-of-control social climber and former wife of the eccentric billionaire H.R. Costigan. Maggie marries an old punk named Tony (Top Cat) Chase, with whom she once had a brief affair many years before, and Hopey takes up with a dull young woman named Rosie. Yet Hopey and Maggie cannot forget each other; they are still best friends and occasionally have sex.
Maggie's marriage predictably ends in divorce, but she still remains apart from Hopey. She gets a job managing the Capri Apartments, a seedy complex in the San Fernando Valley. Maggie also has her hands full dealing with Izzy Ortiz, whose madness gets worse and worse. As Izzy deteriorates, Maggie has her first love affair with a woman other than Hopey. The woman in question is the gorgeous Vivian Solis, AKA Frogmouth, a trashy stripper and would-be actress who drags Maggie into the affairs of her sometime boyfriend, a wannabe gangster named Sid Doan. Maggie does her best to help Vivian and save her from Sid's abusive clutches, but Vivian refuses to commit to her and walks away, leaving Maggie heartbroken. At the same time, Izzy's madness reaches its climax and Maggie begins to see the same fiendish visions that have haunted her old friend for so long. Izzy disappears after her house burns down and she may even have died, though Maggie tries to save her.
In her forties now, Maggie looks like "somebody's mom," but despite much heartache and disappointment she has achieved a kind of peace. The crazed residents of the Capri seem to need her. Hopey has told Maggie that she loves her several times over the years, and Maggie may finally believe her.
When young, Maggie is very attractive and sexy. She gains weight easily, however, and she admits that she eats and drinks beer when she is depressed--which is frequently. Her face never quite loses the prettiness of her younger days, though, and Hopey (who can, and sometimes does, have any pretty girl she wants) has never complained.
Maggie can fix just about anything, but in Mexican society mechanic's work is man's work, and this male attitude often makes Maggie uncomfortable. Like Izzy, Maggie is somewhat torn between her traditional Mexican background (as represented by her family) and the modern American world, as represented by her mechanic career and her punk lesbian life with Hopey. Maggie loves her relatives, especially Esther, but sometimes her family seems to her like "a Mexican Beverly Hillbillies."
Maggie is a devoted comic book fan, and has clearly spent an awful lot of time in front of the television: even while drunk she can remember (and sing) advertising jingles from almost 40 years ago.
Maggie's personality is what finally makes her the warmest and most lovable person in LOCAS. Though never sanctimonious or stuck up, Maggie is fundamentally kind and goodhearted; she may grumble, but she does what she can to help even difficult, unlovable people like Vivian and Izzy. Maggie is willing to believe the best of anyone until proven wrong; the only person she has ever held a grudge against is Terry Downe, and even in that case it took years for Maggie to realize how much Terry hated her and why.
Maggie's loving nature is shown best in her relationship with Hopey, for Hopey is far from easy to love. Maggie admits that Hopey is "kind of a bitch," but she loves Hopey unconditionally and is always willing to forgive her. Maggie's attitude has affected Hopey, too, because Hopey also loves Maggie unconditionally.
Sadly, Maggie never realizes how good she is. Maggie suffers from a lifelong lack of confidence, and she is constantly berating herself for her mistakes and failures, both real and imagined.
With the exception of Terry Downe, almost everyone in the LOCAS world likes Maggie, and she is easy to love. Tony Chase has no bitterness towards Maggie after their divorce, and only regrets that he could not do better by her. Even long after their affairs with her are over, Maggie remains a symbol of a perfect, idealized love to both Ray Dominguez and Vivian Solis.