I haven't spoken to one of my brothers in years (at least a decade) and we have each other's numbers in our phones in case something comes up with our parents. He will say "I love you", when he 'accidentally' calls me rather than a brother, but I refuse to acknowledge. If I am visiting my parents and he comes over, I leave, I do not cause a fuss or ask anyone to make a choice between us, but I will not be in his presence. Yes, what he did is *that* horrific.
To bring it back on topic, my impression is that there wasn't some huge falling out between Jackie and her sister, but more like they just generally rub each other the wrong way. (I am completely open to having that impression corrected, as I don't pay close attention)