Kathy and Jess are moving back to her parents' house. Her family has had a very bad outcome. She, Jess, and Dan are no longer a family; and Dan is not in the picture, although he is the central focus of Kathy's thoughts.
"She could not believe everything that had happened over the last three weeks."
As is often true with bad outcomes, Kathy had been caught up in a snow-balling series of events she neither understood nor could control. Here you see a key to managing your family's risk points. There is a critical point or threshold where you lose control, lose your ability to influence what happens to you and your family. Kathy, Dan, and Jess had reached the threshold three weeks ago; and events are now rushing ahead from their own momentum.
"Possession is the key. Take all you can so he'll end up with as little as possible. She kept reminding herself of her father's statements as she was packing the night before."
You see Kathy has turned to her father to control events. He had told her what to do and she is following his instructions. This is helpful since Kathy is being pulled along by earlier bad outcomes; but you need to wonder how her life had gotten so out of hand. She had been an adult, married, a mother. Now she is a little girl being rescued by her father. The point is not so much that she and Dan are splitting up as that Kathy is not in control, not in charge of herself and her family. This is a key bad outcome to keep in mind as you consider the rest of the narrative.