
It is more so the kind of betrayal that you thought you somewhat knew that person but in the end they lied to you. They were closer than strangers so a bit of hurt you could spare her, even more so it turned out he used her to his advantage to get more inormation in very subtle ways. That's how I see it, but you are right in a way that she is exaggerating it.

No i get that her trust has shaken.Quite normal in her situation but saying that Ian betrayed her is a bit hypocritical seeing as she never trusted him in the first place, stole from him, reported him to a detective of being involved in something shady.She never made an effort to befriend him and neither did he so how could there be betrayal between them

wasn't he the one that sent her best friend (the chef's helper) off, and didn't even bother to tell her that the person she was desperate to find was safe. I think that is a pretty nasty betrayal.
And as for the reporting to a detective, she did the right thing. The dude WAS shady, he was hiding something, and she was spot on, on finding someone who was not acting normally. In that regard too, he betrayed her. He didn't warn her that sh** was about to go sour, and instead, when she could have potentially saved a life, and assisted him, he instead, even KNOWING she wasn't involved, chose to stay silent. Yes. He betrayed her, and it cost someone her life.
I like this manhwa..buuuut.why is the mc suddenly showing such a self important attitude.Ian betrayed you?You were never close enough for that... ( ̄へ ̄)