Well, being super dense like the girl is is only possible in: manga or on purpose. Like, you do stuff without a care about the consequences, don't worry about what's going to happen after you do stuff. She should understand that being this friendly with someone like him is going to make him love her. It's obvious that the MC shouldn't expect her to feel the same, but she should care more about the consequences of her actions.
@Edit: Also very nice we're out of this "arc". I was getting a little tired of the same characters all the time. We already knew the MC had no chance so it's better to introduce more characters/give other characters more screen time.