Vanity, thy name is woman.
The adjective "vain" has two common senses. One of them applies here.
It sounds like Motabariga is a sin of self-importance, the kind of character flaw that leads someone to believe that her (or his) appearance has a far greater value than it does in fact.
Let's see how well it fits:
The word Motabariga (which means something like vanity or self-aggrandizement) is the Muslim Sheiks' favorite word to describe a woman who wears revealing clothes. The word has a negative connotation to it, and is used almost exclusively to attack women who dare to show more skin than custom allows.