(1) Is your mother dead? Your sister is not the executor until your mother dies and your sister is appointed by the court. Before that, she is not the executor and doesn't have to tell you anything.
(2) The executor MUST disclose various things to the court, to the creditors, to the beneficiaries, and to the heirs. But not everything. Besides, most (practically all) of the probate court file is public information.
(3) The disclosures have to made on a schedule. The executor can disclose early, but she is not allowed to disclose late.
(4) There probably are some things that the executor should keep secret, at least for a while. And other reports that cost time and money to put together; she might charge you for those.
(5) You can ask the court to force an accounting from your sister, if she doesn't keep you reasonably informed about the progress of the estate and all the assets. But be advised ... for some things, the court says an annual/final accounting is enough.