It bothers me too how yuuki is willing to do anything to save Zero. And yet she doesn't say that she like him. And she uses the excuse "he's brother", oh come on! that's not a legit reason. She's totally leading him on unintentionally. The words she use towards him and the actions she takes for him, all ref that she loves him. And she's making Zero go coo-coo, cuz of all these crazying messages she sending him.
I mean if a random person was in Zero's shoes, he/she would fall in love with Yuuki too.
