For the enchantress, Yan Yu's side is like a huge harem, and as his official Daoist couple, it's only right that she takes the role of the main wife. Thus, what she cared most about was others' attitudes toward her. As long as Yun Jin showed her respect, she could tolerate her presence.
For Yun Jin, Yan Yu was the person she needed to firmly bind herself to, while she needed to prioritize other people based on their level of threat. For example, simple and naive people like Sister Zhao and Ruoxi, who were also teammates and thoroughly understood each other, would receive much better treatment from her.
As for Ruoxi, Yan Yu was the bad guy who would terribly bully her. Without the help of her sisters, she would be bullied to the point of utter powerlessness; hence, the more sisters, the better.
Although the three of them had different thoughts, their relationship wasn't too rigid, hence they soon started chatting about Dual Cultivation.