What should I do if my period is a week late and I want to go for Umrah, knowing that it is usually very regular?

There is no objection to a woman performing Umrah. If she completes it before menstruation, then that is well and good. Otherwise, she should enter into ihram and wait for her menstruation to end in order to perform tawaf and sa'i.

If she fears that she will not be able to perform tawaf before the end of her menstruation, she may stipulate at the time of ihram: "My place of exit is where I am hindered." In this case, she may exit ihram and depart if she is unable to complete the Umrah, and there will be no penalty upon her.