Marin is a girl of about 13 or 14 whose parents have sent her to live with relatives in Chicago and whose relatives in Chicago would like to send her back to her parents. The adults' motive for wanting to be rid of Marin may very well be that she is trouble, a "boy-crazy" girl and potentially a bad influence on younger sisters and girl-cousins. Marin sneaks cigarettes, dresses seductively, and stares boldly back at boys. She goes out by herself to dances all over the city, probably sneaking out after her aunt has gone to bed and probably pretending to be older than she really is. She is an invaluable source of information on sex, cosmetics, and the ways of men, all those things Esperanza is curious about and cannot learn from books or from her mother. Esperanza's reports suggest that Marin herself, however, is not so well informed as she thinks she is; one suspects that her extreme youth and a sense of honor among the boys and men she dances with — along with a good deal of luck — have so far protected her.
For Marin's precocious sexual maturity is not promiscuity but simply the only way she knows — having learned from the movies and "romance" magazines that young girls of her time devoured — of looking for that magical key to everything: love. The mythic romantic story of true love like a bolt of lightning, sweet music, and wedding bells — popular in Western culture for centuries before Marin, and always ending with "happily ever after" — is what drives her, and she is young and innocent enough to believe it. Even Marin cannot explain why she waited at the hospital for a young man whose last name she doesn't know, but the answer is simple: She stayed with Geraldo out of the pure love in her romantic heart.