Is it permissible for a woman to go for 'Umrah without her father's approval, if her brother approves and accompanies her as a mahram?

'Umrah is obligatory once in a lifetime, according to the preponderant opinion of scholars. Parents are not permitted to prevent their children from performing it if it becomes obligatory upon them, and obedience to them in this matter is not required. However, if the child has already performed 'Umrah, it is obligatory to obey the parents, because additional 'Umrah is a supererogatory act, and the obligatory takes precedence over the supererogatory. It is advised to strive to convince the parent, and if that is not possible and you have not yet performed 'Umrah, there is no harm in going without their permission, as long as a greater harm does not result from it.