In was not oblivious to Oh Ha Ni what people around her think of her.
She can practically hear them calling her dumb, ugly or giving statements like "she's got no chance, she should just give up".
After her love letter to Seung Jo she was determined to stop liking him, and she tried, she really did tried but the more time she spends/live with him the more her plans fail.
As the days pass by, her feelings for him, which she thought were long gone, only grew stronger- she was falling for him-fast.
After their graduation kiss and after she realized that no matter what, Seung Jo would not acknowledge their kiss- it broke her.
She desperately wanted to go-go somewhere far from him- go where no one named Baek Seung Jo existed to break her heart-go where no one would find her or see her breaking, it did't matter where she would go.
She just wanted to disappear- she just wanted-wished she had never met/laid eyes on him on the first place.