I don't think it has anything to do with her father being formally acknowledged as Crown Prince. After all, her parents approved of the engagement when it was first announced in 2017, and by that time it was evident that Masako and Naruhito would not be having any more children. So Akishino's position hasn't changed.

What has happened since 2017 is that it has been revealed that Mako's fiancé is involved in a financial dispute involving 4 million yen. and, probably more importantly, that Mako's fiancé did not inform her about this dispute before the engagement was announced. And the dispute still hasn't been resolved, more than 3 years later.

I haven't a clue whether Komuro and/or his mother are correct in their belief that they don't need to repay the money. But it appears that everybody involved in this mess is more interested in "winning" and being shown to be "right" than to doing whatever it takes to end the dispute and get on with their lives.

Seems we have an answer to the question "What price happiness?" Or at least a ballpark figure: 4 million yen.