What is the ruling of Islamic law regarding a father who utters the divorce pronouncement when angry and then reconciles with his wife, and would the daughter be sinful for not advising her parents?

Your father is abusive in his frequent pronouncements of divorce, and he has already issued two divorces. With the third, his wife becomes irrevocably divorced (baynunah kubra). It is probable that your mother has become forbidden to your father. Therefore, he must be advised to consult scholars to clarify the Sharia ruling. If it becomes clear to your mother that she has been irrevocably divorced from your father, it is not permissible for her to allow him access to her; rather, she must separate from him, even if by a ransom (fidyah). Divorce pronounced in a state of extreme anger is invalid if the person saying it does not comprehend what he is saying.