Both women had things on their minds, especially Shen Yi, even though she now clearly knew she didn't have that kind of feelings for Su Qing.
But watching him and her best friend getting closer would still make her uncomfortable. After all, she still needed Su Qing to recharge herself.
In another perspective, Su Qing was quite important to her. If such a person could be held in her hands, it would be too painful.
So she put in a lot of effort to change his place of stay, tried every way to bring him into her company, and eventually even sat next to him herself.
If, after all these efforts, she suddenly found herself fighting hard on the front line, only to have her best friend steal the crystal, it would be unbearable.
Simply put, it's the possessiveness in human nature acting up, even if she doesn't want it herself, she won't let others have it.
Shen Yi found herself in such a dilemma, even though she hadn't realized it.
