Hernández was counsel for the plaintiffs in Madrigal v. Quilligan (1975), a class-action lawsuit filed by ten women of Mexican descent who were involuntarily sterilized at the Los Angeles County Hospital.

Her grandparents and father, born in the United States, were subject to the forced migration practices of Mexican Repatriation during the Great Depression.

After moving to the United States in 1956 at the age of seven, she settled with her family at the Maravilla Housing Projects of East Los Angeles.

[2] After graduating from Garfield High School, Hernández attended the University of California Los Angeles, earning a bachelor's degree in History in 1970.

[2] In 1975, Hernández was employed by the Los Angeles Center for Law and Justice and immediately became involved with her landmark case Madrigal v. Quilligan, combating the practice of involuntary sterilization of minority women at the discretion of hospital staff.

[6] In 1987, she was fired after being accused of mishandling a major lawsuit in Texas involving discriminatory hiring and promotion practices against Latinos.

[3] Hernández worked on a similar case in California, highlighting the disparities existing between funding for urban and suburban schools.