From Halopedia, the Halo wiki
Before Bornstellar went to Edom, his sister was beginning her mutation from Manipular to first form. When her brother returned nine years later, her mutation was nearly complete and she was being educated in customs for family interchange, courtship, and marriage.
Three days later, on the evening of their return, Bornstellar sat with his sister on the lakeside veranda of their domicile, where she inquired about his search for treasure. Bornstellar was sullen in her presence due to all the terrible events he had witnessed and learned about, while she tried to cheer him up. She informed him about their mother's disapproval of his brevet mutation, but teased that its brutish look would please some of her friends that were slumming amongst other rates. A minute later their mother joined them on the veranda, where Bornstellar revealed some of what he did and was urgently questioned by his sister about Warrior Cryptums, San'Shyuum, and the Flood.
Two hundred days later she was witness to an argument between Bornstellar and their father about his involvement in the creation of the Halos. Her brother was then requested for witness at the trial of the Master Builder, and his sister bid him farewell as he left. Bornstellar did not see her again "alive and free" after the day he left his homeworld.
Appearance and traits
Bornstellar's sister was energetic and inquisitive, frequently asking him about what happened on his adventure. She had admiration for defying Forerunner tradition, and enjoyed teasing her brother about his rebellion against their parents. Although less formal than her mother, her daughter had inherited her trait of looking over her family members with a mixture of appraisal and sympathy. Bornstellar remarked he would never be able to match his sister's innocence and her own thirst for adventure.
Bornstellar's sister was less slender than her mother and in the latter stages of mutation from Manipular to first form. Despite being only twelve years old and six thousand years younger than her parents, Bornstellar's sister was already taller than her mother by a few inches, standing somewhere around 2 and a half meters. On the day that he left for the Capital she wore a ceremonial gown that hovered around her armor, painted blue and silver with streaks of crimson.
List of appearances