Prince Rylen knew this, but he wanted to be a little hopeful that the Royal Family would do what was right and Rose would be treated properly. That she would be given a fair trial and hopefully be acquitted of all the charges. And even if she weren't, there would still be enough time for the crown prince to wake up and end this.
However, this plan was fully dependent on the crown prince waking up. Rylen didn't even want to think about what would happen if the crown prince didn't wake up.
Thomas, however, was bringing something even far more important to his attention—Rose wouldn't go to trial. She would be killed as soon as she reached the capital.
As soon as the young knight said this, Prince Rylen couldn't refute it, not with the Queen's hatred for the young woman. She would be killed, and there was nothing he could do to stop it.