When Mona had to vote, she was not very sure and voted for Palak. Marc told her that he knew it is a difficult decision and since, she was the leader of the week, she should act like a leader and take a firm decision.
Though he did not directly say it, but he made sure he voiced his opinion and was upset that Mona voted for Palak instead of Chetan.
He told Mona that as a leader she should be able to guide the camp at times of such difficult decisions. Mona did not appreciate Marc's defying tone and comments and she simply got up and left the camp area, only to breakdown soon after.