The apartment of Bettina is a very cosy place to stay in Oslo. I just stayed there for a few days, when visiting the university and really enjoyed it. It is easy accessible, shops are close by, you can walk to the university and relax in the evening in the nearby Vigeland park. It was a bit warm, but the temperatures in Oslo were exceptionally high during my stay.
Communication with Bettina was very good, and she arranged everything very well. Highly recommend!