I suspected that the emotional blackmail would be the end of the friendship, except that I thought it would originate on her side. As soon as she said the words, "When once my affections are placed, it is not in the power of anything to change them," I figured that was the end since Isabella has a near perfect track record of failing to do what she says. So for me, the engagement and its bringing them closer came as quite a surprise. But on re-examining her words, it seems likely that Isabella's affection for James Morland will change, too.