Buddhist Burmese categorize Thilashin as tawdwet or ngebyu. A nun who was previously married or widowed before choosing to be ordained is a tawdwet. Ngebyu nuns or young women who are "young and pure," usually virgins that seek ordination as a nun as a profession.
Because ngebyu nuns are considered to have more knowledge of scripture and the practice of meditation that are more accorded more respect that tawdwet nuns.
Source: In Search of Buddha's Daughters by Christine Toomey
When the Buddha's mother died suddenly seven days after his birth, the responsibility to raise him fell to his aunt. After he established his monastic order of monks she came to him with a request to create a parallel order of ordained female members of the Sangha. He refused her first request but later changed his mind. The first order of ordained women was created, separate from the male order and under the leadership of Buddha's aunt.
These women became Buddhism's first order of nuns. There where twelve apostles and they are regarded as Bhikshuni saints. Buddha's aunt Mahaprajapati became the first woman in Buddhism to become an Arhat (enlightened one) and many of her apostles achieved enlightenment.
