Katrín received the Blackbird Award, an Icelandic crime-writing prize, for her first novel, Dead Sweet in 2020. Her debut novel was reviewed well by critics and hit the best-selling lists in the first weeks after publication. Katrín has a political background and was a member of Parliament from 2003 until 2016. Before she was elected to Parliament, Katrín was an advisor and project manager at a tech company and a senior buyer and CEO in the retail sector, as well as the Managing Director of a student union during her uni years. She worked from a young age in the fishing industry, as a store clerk and took nighttime shifts at a pizza place. She studied Anthropology and has an MBA from Reykjavík University. She was raised in Kópavogur, about 15 minutes' drive from downtown Reykjavík. She now lives in the neighbouring town of Garðabær with her family. She is married to author Bjarni M. Bjarnason, who encouraged her to start writing. They have four boys.