She felt fake before her best friend because she was pretending to be unaffected by how Kihyeon was affecting her life in her eyes. Kihyeon's presence in her reality made her feel powerless, as if she was unable to make friends on her own, have her own effect on people, as if he drove people away from her. But because of what her parent skept telling her, she was repressing those feelings, bad feelings.
From Kihyeon's perspective, everything he did was so that Gaon wouldn't have to trouble herself with anything, or anyone else other than him. He wanted to have Gaon all to himself, and that way he thought that he would be the most important person in her life. But Gaon doesn't see things this way, that only drove her away. Gaon needs freedom and a sense of self, she doesn't want to depend solely on Kihyeon. She doesn't connect in that way.
Wait i dont get it. Was she insecure? She felt fake because????