A little bit of a rant. Note I have read the novel and I do like the story, and I kinda agree with you when it comes to her self confidence. But Aqua should remember that Tiara's been thrown away before. He doesn't know about the game, but he should probably realise that she's wary of other women when it comes to people she loves. She was basically cheated on then thrown away, game or not that fucking hurts my dude and all that self doubt and worry doesn't just go away when a nice new mans comes along, even if you know that they love you. It also doesn't help that she knows that this was a game and COULD lead to the same thing happening to her a second time. The way she's handling it is a little aggravating, and I definitely don't think she should run away when Aqua fell in the fountain then serve tea to the fairy King, but I also think Aqua should be a bit more proactive in the fact that he's already realised that Tiara is nervous about his relationship with Aishira, whether or not it's just work or something more.

Tiara, ugh! It’s not the game, it’s you who’s bringing about self destruction. Her man falls in a fountain, another woman is wiping his face and she runs away, crying. The Fairy king, whom she knows has an interest in her, takes advantage and she serves him tea. No game could’ve done the damage she’s done. Thanks to her behavior and secretive nature, Aqua is doubting her love for him. Not to mention her actions that will cause chaos with the Forest Fairy kingdom.
Who’s left to comfort him? Asahira. She served her man to her on a silver platter. Don’t get me wrong. I still love my sweet Tiara, but she’d better get her **** together because right now she’s a train wreck.