HIPAA violations may no longer apply now that she is deceased but if this is truly concerning medical malpractice, it may not be sufficient for you to show the death certificate to the medical provider and your documentation showing you are the legal representative. You have to be entitled or obtain entitlement to those documents and that may require you to subpoena those records. Document production requests can be quite complicated but generally speaking you will either most likely need an attorney to help you obtain those records or you will need to file a lawsuit as the representative of the estate and through the suit submit the subpoena.