She was the beacon of hope for all Mexican immigrants, as she led her music in a triumphant march from the ghettos to the soccer stadiums: Selena Quintanilla-Pérez. Overnight, she became the queen of “Tejano,” a blend of pop, soul, and Latin rhythms. But no one had prepared the young woman for the dual role of being both a beacon of hope for the poor neighborhoods and the courted darling of the ruthless commercial machine.