Izzy is Mexican-American, and she grows up in Huerta (Hoppers), California. She has an older sister (Chabela or Chela), an older brother (Big Eddie), and a kid brother (Eulalio, or Speedy). She is particularly close to Chepa, one of her female cousins.
Izzy is a slender, dark-haired woman. In her youth she is quite attractive, but as her mental problems become more serious they take a toll on Izzy physically and she also neglects herself. In her forties, Izzy looks at least ten years older than she really is. In the 1980's, Izzy wears her hair in disorderly braids and dresses mostly in shabby black clothes.
As a child, Izzy babysits a smaller girl, the young Maggie Chascarrillo. As she grows into a teenager, Izzy enters the girl gang scene. Together with Chepa, she is one of the founding members of Las Widows, Hoppers' most fearsome female gang. At the age of 18, however, Izzy is arrested and injured by a knife attack while in jail. This drives her to reform herself, and she finishes school and goes onto college, where she studies literature. Izzy's father wants her to become a teacher but Izzy decides to be a writer instead, and she and her father fight bitterly.
While she is in college, Izzy also falls in love with her English professor, Jack Reubens, who is much older. The marriage is a disaster. Izzy gets an abortion and she and Jack quickly divorce. Izzy is already part of the punk scene, but her traditional Mexican-Catholic upbringing gives her a great burden of guilt over her abortion and divorce and she tries to commit suicide.
Izzy goes to Mexico to try and forget her troubles but she meets a man with a child there and becomes involved with him. Izzy gets pregnant by the man and the two plan to marry, but Izzy begins to see visions of demons and the Devil. After another abortion, a frightened Izzy returns to Hoppers when she hears that her father has died.
After coming home, Izzy ceases to care for her appearance, becomes obsessed by the occult, and plunges deeper into drugs and punk. Her behavior becomes more and more eccentric, and local kids call her "The Witch Lady." She moves into a house that is said to be haunted, and she continues to see visions of ghosts, demons, and so on. It is never quite clear whether these visions are real or simply the product of Izzy's psychosis. Izzy may be second-sighted; while in the hospital, she sees (or claims to see) events through Maggie's eyes, though Maggie is far away in Texas at the time.
Izzy appears to be entirely heterosexual, but her experiences with men are unhappy and her personal demon claims that Izzy has a grudge against the entire male sex. Unlike Hopey, Maggie, and Terry, Izzy shows no lesbian inclinations, but after her trip to Mexico she seems to lose all interest in sex.
Tragedy continues to stalk Izzy. Her beloved kid brother, Speedy, kills himself, and some time after this Izzy is briefly institutionalized. In the 90's she is institutionalized again, apparently after yet another suicide attempt (she is shown in the hospital with bandaged wrists). Despite these troubles, Izzy continues to write, and eventually has some success. Some of her work is published, but Izzy is too paranoid and self-doubting to handle the strain of book signings and talk show interviews. She eventually becomes so hostile and erratic that even old friends like Maggie and Hopey find her hard to deal with. Izzy finally disappears when her house burns down in a fire that she may have set herself. She may have run away to Mexico again, but this is not certain.
When she is not obsessed or paranoid, Izzy is a highly intelligent woman, and her slightly greater years and experience have given her more wisdom and insight than the other Locas. Helpless to understand herself, Izzy is very perceptive about others. She cares deeply about Maggie and Hopey, and feels a special sense of responsibility for Maggie's safety and happiness.