She failed to kill Sasuke because her love for him is selfish, when she talks about her love for him it's all about her feelings in much the same way that Hinata talking about her love for Naruto is all about her feelings for him. SasuSaku isn't going to happen because of this reason.
thank you we know itasaku won't happen, it's a crack pairing, it's for fun. anyone who takes it too seriously needs to rethink how the manga is going