What is the cause of the problem between Jordan and Nick?

After all that had happened the night before (Myrtle's death), Jordan focused on how she believed Nick treated her the night before. He saw her comments as selfish and unfeeling.

"I've left Daisy's house," she said. "I'm at Hempstead and I'm going down to Southampton this afternoon."
Probably it had been tactful to leave Daisy's house, but the act annoyed me and her next remark made me rigid.
"You weren't so nice to me last night."