Unfortunately, if you go by ancient history. With noblewomen and royalty such as princesses and queens, women did not have many rights and privileges. One of the main factors I I did brought last year that women were not to meddle in the affairs of men. One thing I see common in Asia history, is that noble and royal women is some nation and cultures are only allow to have one spouse per lifetime, meaning that they have "no privilege" to divorce their husband and will be charged in the act with capital if caught fornicating or proven that woman is in an intimate relationship with another man or person other than her spouse. This also implies if they becomes widowed too. Only way to annul is the woman's husband divorces her or the woman's sire seeks audience to his country's sovereign for an annulment, which mostly means and of alliance between noble clans or other countries (royalty).
Now onto the story. Before Cassandra could be void of an marriage with Lance, she was given ultimatum that the council will appoint her a new husband of their choosing as part of the CRA (Clan Restoration Act) program or forever hold her peace. She outrageously decline and did not wanted to get marry to anyone else ever again (that was before Alphonse) , so it was set in stone. Obviously, Vanaheimian regulations are non existent here in our modern world of Midgard, home to over 7 billion human inhabitants with Isis being a major headache along with some of the worldwide presidents. In America, she has a a certificate, prove of marriage with Lance.
It happened when she got caught during war time having an affair with Alphonse. Instead of receiving the death penalty, she was exiled never to step foot into her home world ever again. Living in Midgard, she has to same privileges like you. She can marry whoever she wanted and be treated equally as men. If she were to return to her homeworld, she will be charged with multiple accounts of capital offense, which include bigamy because in her world. She is still legally married to Lance and Eddie in the world will be treated ans an illegitimate child.
Will continue the rest when I wake up