Since 15th century, properly 1470s, Vietnamese women had already had the rights to break engagements and to divorce, according to Hong Duc Code of Le Dynasty.
According to Women's Movements in Asia: Feminisms and Transnational Activism by Mina Roces,Louise Edwards: "According to this code, it prohibited marriage without the woman's consent; even after an official annoucement, a woman could break her engagement if her future husband was deemed critically ill, found guilty of a serious crime, or if he squandered his family property. After marriage, a wife could divorce her husband if he abandoned her for more than 5 months, or, if the couple had children together, after a period of one year. A man could not simply divorce his wife on the grounds of illness, neither could she be divorced if she was judged guilty of a serious crime. Furthermore, a married was guaranteed protection from enslavement and had the right to inherit property from her family."
FYI, the Hong Duc Code was the only feudal code in Vietnam that recognized the women's role and some degree of equality between men and women and determined women's civil legal capacity (Articles 308, 322, 375, 388, 391…).