A lot of that has been discussed previously in the thread.
Yona has lost that spark and that passion. She challenged the chief for the truth of what happened to her father and lost, thrown off a cliff. If she died, then there could be some honour claimed; she tried, she failed, she died. She could live with that. As it is, she gets rescued by a guy who had previously just magicked a pool into his floating house.
I would imagine that in her mind, Yona has failed twice. She failed when she lost the challenge and she failed when she didn't even die right. However good the MC's intentions, he's dealt her a grevious wound to her pride/honour/whatever you want to call it. He's taken that from her and in a way has made Yona his. She outright says that he basically claimed her as his wife when he rescued her, so she'll do her wifely duties, as in lie back and become a living onahole.
So, as I've said before, I suspect that Yona's arc is going to be about the MC and the others trying to relight that fire and maybe get her back on her feet. Preferably in a Rocky 3 style montage.