The convicted killer was pronounced dead at 3:40 a.m. on Friday at an outside medical facility after being transferred from the California Institution for Women on 18 April.
Broderick was serving 32 years to life for the 1989 shooting deaths of her ex-husband, Daniel Broderick, 44, and his wife, Linda Kolkena Broderick, 28.
The San Bernardino County Coroner will determine the official cause of death. Her case drew national attention and inspired a book, two TV movies and a television series.
Amid a federal probe into prison abuse, was Betty Broderick's death from natural causes or a symptom of systemic neglect?
After decades of infamy as a 'woman scorned,' does her death in prison finally bring justice for her two victims?