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I am very sorry to learn of your sister's death.
Unfortunately these cases are difficult to prosecute ("wrongful life" cases do not typically garner very much in damages claims, and you must retain a lawyer to prosecute the case - you cannot do this "pro per" (without a lawyer)), and you have already made the appropriate complaints the governing agencies so that they can investigate and take administrative action.
However, you can speak with a local personal injury attorney (also called "plaintiff's lawyers" or "trial attorneys"). Fortunately the majority of these attorneys will provide you with a free consultation, and many will represent you on a contingency basis (they will advance the costs of litigation and legal services in exchange for a portion of your successful settlement or judgment). You can find local attorneys using the State and Local Bar Association directories, or private directories such as www.AVVO.com; www.FindLaw.com; or www.Martindale.com (I personally find www.AVVO.com to be the most user friendly).
While this may not be an ideal case for litigation, it may at least be worthwhile to pursue something in mediation, and a lawyer should be able to assist you in getting the pre-hospital medical records.