Question: What is the date of death of Irene Ibsen Bille's mother?
Sentence (from "Irene Ibsen Bille"): She was a sister of Tancred Ibsen, paternal granddaughter of world-famous writer Henrik Ibsen and Suzannah Ibsen (née Thoresen), daughter of Bergliot Ibsen (née Bjørnson) and maternal granddaughter of Bjørnstjerne Bjørnson and Karoline Bjørnson (née Reimers).
Relevant evidence: Yes