She....she was so stupid for 9 10ths of the manga
She was an introvert with bad or none experience. Her family was not giving her attention, a boy she interacted in school was actually a real dick, and she lived and worked always alone. Good thing she managed to have friends but socially she was inadequate. Plus she thought that if she tell him that she loves him he would lose interest. My actual complain with her was when she break up with him. I realize her troubles but she didn't sit and talk with him about it
I really don't like where this mangamis going. I mean he's saying no. Basically forcing that slime on him