Seems that she might have a pretty low self-estem and to add she is almost emotionless. However MC influence somehow started to crack her heart. Anyway im afraid they won't be together in the end, the age difference is probably close to 20 and i can see her rejecting him harshly at some point or even switching schools or just leaving the place without telling him, then he might end up with the "flat chested" girl in the end (she might even confess at some point but he rejects her at that time)
I would like to see some of her past, was there something that made her be like this?