She started her acting career in 1945, and is probably best known for her role as Valborg Jensen in the Olsenbanden movies, as Marve Fleksnes' mother on the long-running Norwegian television comedy Fleksnes Fataliteter and as the janitor's wife in the comedy film Skulle det dukke opp flere lik, er det bare å ringe (based on the play BusyBody by Jack Popplewell).
Haagensli is probably most known for her role in Fredrikssons fabrikk, where she played with Elsa Lystad, Anne Marie Ottersen and the deceased Aud Schønemann, among others.