For someone with that much power and potential, Thorin thought Riona was really naive.
When Riona came up with the suggestion of a wish for the winner, he thought she would ask for a more substantial request. He was disappointed to learn that her suggestion was pretty trivial.
Recalculation of the Nightwarden Trials result? He understood that she was confident in herself–in her performance, and it was justified.
However, her wording left a lot of room for more sabotaging. Riona could've phrased it better, like demanding to be in the Nightwarden no matter what.
An unconditional inclusion as a Nightwatch Novice would definitely secure her position.
Princess Lisbeth, on the other hand, seemed to know what she was doing. Her decision was in sharp contrast with Riona's reckless choice. It seemed as though the princess had anticipated Riona's suggestion and deliberated thoroughly before voicing the wish.
