Insurance Company won't honor Simultaneous Death Act

My sister committed suicide two days prior to my mom's death but her body was not found until two days after my mom's death. My mom's annunity insurance company says they do not have to abide by the uniform simultaneous death act which clearly says my sister should be considered to have predeceased my mother since her body (date of death certificate) is less than 120 hours from my mom's death. The insurance company can produce no proof that they do not need to pay to my sister's estate. I have produced a corner's report which clearly states that the evidence points to my sister's earlier death but the laws of California require them issue the death certificate on the date her body was found. My brother, other sister and I are the remaining beneficiaries and should each receive 1/3 of the proceeds rather than 1/4. We are in a stalemate. I don't know what to do now.