Dude fell in love with how she is, who she is, so it's pretty safe to say she doesn't need to change massively. Otherwise he wouldn't have noticed her in the first place. On the other hand, if you consider their early meetings, he must have felt that she hardly paid any attention to him. Even when he was half naked in ch3, she was acting all nonchalant and calm. So, he probably got the impression, like he mused earlier in ch2, that she wouldn't see him as a man at all. That would drive him to act more mature.