She is the daughter of Johan H. Andresen Jr., owner of Ferd AS, who, in 2007, transferred 42.2% ownership stakes each to Katharina and her sister Alexandra. She is the great-granddaughter of Johan H. Andresen, great-great-granddaughter of Johan Henrik Andresen and Anton Klaveness, and great-great-great-granddaughter of Nicolai Andresen. Johan Henrik was the brother of Nicolay August Andresen, and the uncle of Nils August Andresen Butenschøn.
In November 2017, Andresen was fined 250,000 kr for drunken driving. Andresen's blood-alcohol content was three times the legal limit. Alongside the fine, the sentence included 18 days of imprisonment and a 13-month license suspension.