What if she doesn't outlive Paul, or not by much?I don't really know if that alone would do it. After the Apostasia in 1965 he pissed off a lot of influential people, namely the Papandreous, perhaps that injustice combined with any perceived tolerance of the Colonels would be enough to make them call for his throne after 1974. You'd also have to butterfly Queen Fredrika out of the scene to get Constantine to grow a pair because she pretty much ran him like she ran (to a much lesser extent) her husband the late King Paul.