well according to the manga im reading.....Karin seems to be the only logical answer seeing as Sakura hasn't been shown liking Sasuke since the beginning of Shippuden..and Sasuke has never ever shown interest in her. Sakura was willing to kill the one she "loves" in order to make Naruto happy...seems like a confused kuniochi to me who doesnt know what she wants. Hinata sure as hell wouldnt kill Naruto to make Kiba happy would she?