Is a wife obligated to obey her husband in spending the vacation with his family, given the presence of her elderly father who needs her care, and her assistance to her sister who is looking after him?

The wife must obey her husband by staying with him for the duration of the holiday if he does not approve of her staying with her father. However, there is no objection to her trying to persuade him to allow her to do so. If he insists on refusing, then obedience to him is obligatory, and there is no blame upon her as long as her sister is serving her father. She will be rewarded for her obedience to her husband and her intention to serve her father.