You argued it wasn't Aya's intent, and is it betrayal if it's unintentional?
Sure thing. Even if she didn't intend to betray Hikari, she still knew it would be a betrayal to kiss Yuu there.
Seems like Hikari wants to parse out what happened before she makes an accusation she can't take back. What's normal for you isn't necessarily Hikari's confrontation style.
I mean, sure, but that just adds another point to her goody two-shoes account. She can never do a wrong thing. Even when faced with betrayal by her best friend, she goes for a peaceful option. It's not in her style to have conflcts. She'd always carefully listen to the other side, try to defend them from accusations, forgive them.
These are all good qualities, don't get me wrong. But when a character is all about good qualities, it just doesn't work for me.
Which to get back to the original argument - you think it's unrealistic for Hikari to not start w/ being mad about the betrayal, and I claim that by your standard it's unrealistic that Yuu didn't start off w/ being mad at Aya for ranting at him after she ghosted him.
This all started with you claiming that Yuu is being more of a goody two-shoes than Hikari. It was interesting to discuss some aspects of his reaction vs Hikari's reaction, but the initial argument is just hopeless. We just saw Yuu lying to Hikari, using underhanded methods to probe her reactions, hiding his relationship with Yami from everyone, lying to his family, being weak-willed and passive - and you really intend to argue that he is more of a goody two-shoes than Hikari?