Her sister, Guðrún Þorsteinsdóttir, was married to the chieftain Kolbeinn Bjarnason, but Hallbera's marital status prior to taking the habit is not mentioned in contemporary sources.
She could have lived as a financially independent widow before turning to a religious life, as was not uncommon for aristocratic women in Iceland at the time.
In 1295, Hallbera donated vast lands to the foundation of a convent for nuns of the order of Saint Benedict.
If Hallbera and Sister Kristín are the same person, then she lived at Munkaþverá as a nun or anchorite prior to the founding of Reynistaðarklaustur and was an educated and literate woman for whom the religious name Katrín (Catherine) would have been highly appropriate.
Hallbera had a close professional relationship to the Bishops of Holar, Auðunn rauði Þorbergsson and Lárentíus Kálfsson, who respected her opinion.