"You should also know that the kick is personally ordered by my boss. Vernon said I should kick you for slandering his beloved woman," Diamond said, adding salt to the injury.
Because it was a clear sign that Vernon hated her, and there was no way for them to reconcile and become a pair of lovebirds again.
Shailene was still in both physical and mental shock after getting kicked in the face by Diamond. She was still trying to process what was happening, then started regretting all the decisions that led her to this condition.
Had she know that she would be disgraced like this, with her deepest secret getting dug out, she would never stay in New York.
Diamond was finally satisfied, looking at the despair in Shailene's eyes. She loved seeing this bitch break down both physically and mentally. After all, Shailene didn't seem to be bothered when she said all those horrible things to Erik, the boy she killed with her words.