She also said that she loves Duck more than life itself. Which is a pretty normal line in well, normal context, but in that situation I really thought that she will not come back.
Katjaa also did not seem like she was used to the situation...I mean she probably just looked over the kids, nursed the sick and...well I do not think that she went out on supply hunts. I mean she really does not want to use a gun, probably never even trained to. And then everything fell apart, starting with the farm, than the motor inn and finally her son. I can understand her.
And yeah...she appear broken when you tell her the truth about what happened to Larry. Maybe she wanted to die with her humanity left...and not being forced to do stuff like Kenny to survive.
We'll never know.