This was all a lie.
Xu Rong'er couldn't find anything else to tell her brother. So, she made up a lie like that.
In truth, she wasn't planning to marry Chu Munan anymore. A weak woman like her needed someone that could protect her, and she was confident that it's not Chu Munan.
….
The event with Xu Rong'er didn't really have any effects on the mansion. When Xu Rong'er left, Chu Munan stayed. He didn't even bother stopping or comforting Rong'er when she left.
After that, Chu Munan just stayed around with his brother and Cleo and Rue.
"How could you stay?" Cleo asked Chu Nan. "I thought you are already planning to leave?"
"My brother is staying. I can't leave him here."
"Why are you treating us like we're bad people!?"
"You are bad people!"
"Humph!" Cleo crossed her arms across her chest.