It's very obvious to me that Asami has got claim of THE DICK and there really isn't much that Maako could even say otherwise, so she instead has to create this weird conflict of not wanting to bring her sister's mood down with the reveal that he has feelings for her. It's pretty weird, I would've assumed that a gyaru put that situation would have no problem being all like, "LOL bitch that dick was mine from the start, find yourself another man or wait till I've have my turn with him." Something along those lines. Either way I hope like translator-kun said that she'll get some more confidence and get to chasing him more aggressively.