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.
Authorities responded to the casino after reports of an unconscious woman in a bathroom. Assad was transported in serious condition.
Anyone with information regarding the case is urged to call (951) 696-3000.