Has the daughter sinned against her father by disobeying him in choosing her university major and causing him to be angry with her? What is the way to correct her mistake and make him proud of her after his death, knowing that her mother holds her responsible for his death?

The contentment of one's parents is among the best acts of proximity [to Allah]. Therefore, whenever a child can fulfill what his father desires of him in matters of study, it is better. However, obedience to parents is not obligatory in every situation. A son is not required to obey his parents in entering a specialization he dislikes. There is no sin upon him if he goes against his father's wish in choosing his academic specialization. He should, however, strive to honor his father after his death.