It's not about being a "real" fan, it's about observing the scenes the pair share with one another. Alto gives her advice and has shown sincerity and concern for her well-being...you can take that as a more brotherly approach or the potential to have something more grow from it. Ranka isn't 100% oblivious to how Alto is as a person and to his personality; she's just rather naive and thinks she can have her cake and eat it too without some compromise. I see Ranka getting hurt in the future, either it be with her strained relationships or what have you, but it'll make her grow. At least, I hope we'll see such developments.