She is going about this entirely wrong.
When he said she doesn't love anybody, she just has to admit she falls in love too, but because of this screwed up world, the guys always run off with other guys.
She's a victim of this world, and she should have told her brother to his face that she is. This world is even uglier toward women than the real historic world was, after all. And to be expected to just give birth to a kid and hand him over to be raised by the 'royal couple' as the heir? Men get to love who they want but women are just birth machines? All the RL women I know would have noped out of there a long time ago. Head somewhere else and let the royal family die off. It's for the best.