Why had nora not seen her friend kristine linde for many years prior to the action of the play?

It was because Kristine Linde’s husband passed away a few years earlier, and she was left with no money and no children. She also had to take care of her sick mother and her two younger brothers for years. While Nora and her husband were very poor and both had to work long hours but her husband became sick and they had to travel to Italy so that her husband could recover.