The first kill could make Sakura more determined. It gives her a taste of the real challenges in the shinobi world. She may then focus more on her training, aiming to become stronger so that she can face future threats without hesitation. It could also make her more cautious, as she now knows the gravity of the actions she is taking in the dangerous Land of Waves.
Sakura may become more empathetic. Killing someone, even in a fictional context, can make a character understand the value of life more deeply. She might start to see the enemies not just as faceless foes but as people with their own stories. This could lead to her trying to find non - violent solutions in future situations whenever possible.