Investigators say Olivia Culbreath, 21, of Fontana was speeding against traffic when she collided with a Ford Explorer near Philips Ranch Road on Feb. 9.
Kristin Melissa Young, 21, of Chino, and Culbreath's sister, Maya Louise Culbreath, 24, of Rialto, were both killed in the incident. Both were passengers in Culbreath's Chevy Camaro.
All four people traveling in the Explorer were killed. The four family members were identified as 47-year-old Gregorio Mejia-Martinez, 42-year-old Leticia Ibarra, 20-year-old Jessica Jasmine Mejia, and Esther Delgado, all from Huntington Park.
Culbreath suffered a broken femur and ruptured bladder following the crash. She remains hospitalized at the jail ward at Los Angeles County USC Medical Center in lieu of $6 million bail.
Culbreath was previously convicted of DUI, according to the DMV. Her license was suspended in January 2010 and she was convicted in April 2010. Her license was reinstated in December 2011.
If convicted of the latest charges, she faces a maximum sentence of life in state prison.