Cathy doesn't want to be the one who is always responsible and in control, especially now that she has been diagnosed with a terminal case of melanoma. That's why she kicked Paul out of the house as she literally wants to be the one in their twosome who is seen as the person who freely spills wine on the sofa without caring, instead of that person always being Paul. That's why she's decided that she wants a pool built in their postage stamp sized yard, so that she can teach Adam how to do the banana split dive like she did when she was his age. That's why she feels that she can give Adam a taste of his own medicine by treating him as thoughtlessly as he seems to treat her, all in an effort to make a point. That's why she feels that she can be blunt instead of being politically correct to her student Andrea about the combination of her wisecracking and her weight. That's why she decides that she doesn't need to be cordial anymore to their crotchety neighbor, whose name she doesn't even know after living next to her for five years. And that's why she tries to reach out to Sean despite Sean abhorring everything about what he sees as Cathy's chosen bourgeois lifestyle. Regardless of these changes, Cathy isn't yet ready to tell anyone, let alone her family - Paul, Adam or Sean - that she is dying.