Its not that easy. She could use kunais at any time and was fighting Ino seriously (even throwed some at one point). She didn't have to kill her, just injure would be enough but she didn't do it (or couldn't).
Sakura's 'feats' at that time could be replicated by any genin (except chakra control, genjutsu skills and amateur medical ninjutsu) given her overall lack of physical attributes and abilities (Iruka even made a remark on this after Team 7 finished the 2nd stage of the CE), that's not the way.
Rin is featless but the difference between Chunin and Genin was made very clear in part 1. There's a reason why Sakura didn't pass the exam the first time, on the other hand Rin managed to get there faster.