She maintained her elegance and didn't explode in anger whenever she saw Lu Xiuse.
Wei Wucai was observing her carefully.
He could tell that Yan Zhiqing would only reveal her true character when she was around people she trusted.
With people she trusted, she could laugh like there's no tomorrow and rage and roar without any worries.
Yan Zhiqing would never show these expressions in front of people she did not trust. She would never reveal her true character to people she did not trust.
And so, Wei Wucai knew that Yan Zhiqing had always trusted him, even during the time when she was always arguing and fighting with him.
If not, he would have never gotten the chance to see Yan Zhiqing mad.
Wei Wucai also thought that Yan Zhiqing had an interesting personality.
If he was with her, he would never feel bored.
He knew about microexpressions.