Funny how thoughts change as characters develop. Last chapter I was cheering Youko to fight on. Now I'm not even sure at all if I want her to end up with Nana. Nana seems immature and short-sighted, and I can't for the life of me figure out how Youko fell in love with someone who just keeps hurting her (obviously there's more to each character, and we don't choose who we fall in love with...I just don't follow is all).
IMHO, sometimes you just fall in love with the person who is most important to you. in Youko's case, Nana was that person. as for Nana's immaturity, well... OK, she had a crush on Tsukiko and to a lesser degree had those emotions/feelings reinforced and validated by the manga she was reading. when her heart gets hurt, she immediately dismisses the whole thing as "onee-sama play" because it is easier to dismiss those feelings than have to admit that your heart was broken, and I don't think that is completely an immature thing to do as many of us do it when we cannot get our way.
Also, notice that Nana is crying here. question that should be asked, is she crying because she hurt her best friend's feelings, because in that instance she realizes she is really in love with Youko, or both?
Finally, some may call this story and especially this chapter cliche, but I kinda like that the drama was forced to move the story along. truthfully, I don't think I could have taken another chapter or two of Nana squealing over Tsukiko. plus, it allows Takamiya-sensei to explore Nana's feelings and how Nana might come to the realization that she really loves Youko (assuming they end up together).