Sungah is not a bitch, don't overreact, like said someone here, with sungah's experience with the psycho one ranchat, she developed like an "armor", to proect herself, plus, she doesn't know that Joonwoo protected behind her, she just knows him like a "friend of my class" not less not more, and more, the MC can be see as strange, he doesn't speak at all, just looking and answer quickly, he hesitates. I think Sungah scared about a second "crazy love psycho man" like the four eyes guy at the beginning of story