What should a woman do if her stepmother tells her that she doesn't want her father, and her father hears that?

The intent of the question is unclear. If it is about divorce occurring simply by a wife's words, the answer is no, it does not occur, because divorce is in the hand of the husband. If it is about the correct action in this situation, then it is obligatory to remind the spouses of their rights and duties, and to advise the one who has fallen short among them to fear Allah. It is not permissible for a woman to seek divorce without cause, for the Prophet, peace and blessings be upon him, said: "Any woman who asks her husband for divorce without any cause, the scent of Paradise will be forbidden to her." If the wife dislikes staying with her husband, she may seek khul' from him.