Why did Su Qingyi shoot Lin Jinghao in the novel 'Limited Edition'?

In the novel," Limited edition man," Su Qingyi shot Lin Jinghao because Lin Jinghao harassed and threatened her after shooting her boyfriend. Su Qingyi felt despair towards Lin Jinghao, thinking that Lin Jinghao had already posed a serious threat to her, so she chose to shoot and end her life. However, at the end of the novel, Su Qingyi also realized that her choice to end her life was wrong and hoped that Lin Jinghao could recognize her mistake and give her a chance to start over.