Kimesha Monae Williams, Leonard's sister, is being held without bail at Indio Correction Facility.
Afaf Anis Assad, 84, of Long Beach died Wednesday after being found unconscious at the Temecula casino, deputies said.
Assad is believed to have been the victim of an assault on Aug. 31, according to Riverside County sheriffs.
Authorities arrested two female suspects believed to have been involved in Assad's death. Williams, 35, of Moreno Valley and Candace Townsel, 39, also of Moreno Valley, were arrested and charged with robbery and murder. The defendants are being held without bail because they have been charged with murder with a special circumstance that makes them eligible for the death penalty, according to the Riverside County District Attorney's office
Authorities responded to the casino after reports of an unconscious woman in a bathroom. Assad had gone to the casino with her husband of 60 years who was waiting outside the bathroom for her to come out. Assad was transported in serious condition.
Kawhi Leonard signed a $100 million contract with the Clippers in July.
Anyone with information regarding the case is urged to call (951) 696-3000.