Estelle was the easiest bunch to be manipulated. She spent her entire childhood hating the corrupt noble. And suddenly a "good" king acknowledge her talent and even making her a knight commander, something a woman has never achieved before, of course she became his mad dog.<br />Did Khalid ever talk to her about this and she ignored him? If not, then it is not justified for him to kill her, otherwise Khalid wasn't in the wrong. A stubborn dog is even worst than her evil master.