Dark Triumph - Book 2 of His Fair Assassin series

When Sybella arrived at the doorstep of St Mortain half mad with grief and despair, the convent was only too happy to offer her refuge - but at a price. The sisters of this convent serve Death, and with Sybella naturally skilled in both the arts of death and seduction, she could become one of their most dangerous weapons yet. But her assassin's skills are little comfort when the convent returns her to the life that nearly drove her mad.
Her father's rage and brutality is terrifying, and her brother's love is equally monstrous. But when Sybella discovers an unexpected ally she discovers that a daughter of Death may find something other than vengeance to live for .