I suppose she likes him, cause at start he was like that weirdo who wasn't after her, and her curiosity/ego made her watch him, and from watching him she slowly got somehow hooked?
Thou the big-dude didn't go after her either so not sure about that theory.
First few chapters kinda make me recall the Listless Tanaka anime. Dude also had big bro, who would actually carry him like a damn bag, and also the best looking girl in school gone after him. Part both Tanaka and said girl have more "character depth" if you will. With the girl having "secret persona" of her being her normal non-beautified self, and dude at least talks more.