ANSWER:

If there is no one to help them for real, this becomes an obligation upon their daughter and she must do that even if her husband divorces her. 

She should be diplomatic with him and try to convince him peacefully. 

QUESTION: I know that a wife is supposed to obey her husband in Islam. But if a husband doesn’t allow his wife to meet her parents even if they’re in critical condition and may die if they don’t get help, should the wife still obey him? Will she be sinful for still going to her parents to help them? If yes, then plz explain why.