It is difficult being a young person and going through a major break-up no matter who you are. I would bet that it would be even more difficult if you were famous and engaged to an even more famous person. Here is Jane announcing to the world that her engagement and relationship to Paul McCartney is over.
On July 20, 1968 Jane appeared on the show "Dee Time" and said,
I haven't broken it off, but it is broken off, finished.
And after that, Jane chose never to talk about her relationship with Paul again.