I Have the feeling these fucker plan was always to use her as a scapegoat to trigger the war.
They deserve to be flattened.
BTW her parents never understood that if the world peace stand on the shoulder of a single person, they already failed, becouse that's a pure illusion. The ones who push for war won't be stopped with a single person, not with an arranged political marriage.
Thinking otherwise is stupid, and just show they aren't suited for ruling a nation at all. It could work if the tensions are accidental, caused by border incidents, immigration, trade,etc, but not alone, and especially not when tensions become the ontological reason to be of a nation.
Also a nation that want to start an offensive war, generally prepare for some times. For a real history comparison, between Hitler become chancellor of Gemrany and the attack on Poland passed 6 years.
If the nation have a semi competent spy network, catching sign of the paradigm shift to increase military personnel and supplies is not that hard, and that should trigger an alarm, especially if there are already tensions.
So either the country don't have a decent spy network, or the king is incompetent enough to not even consider the possibility, even after being told. In both cases they are bound to fail.
Granted the queen was right that the marriage could not be annulled. However they could send someone to investigate that claims and provide a safety net for her in case.
Unless it was all a ruse and they wanted to trigger the war too, and were willing to sacrifice their own daughter for it.