Luo Yixuan's current situation was that her Divine Sense was only at the level of a cultivator who had just achieved Foundation Establishment.
However, her body was full of Yellow Springs Spiritual Power, reaching the realm necessary for Core Formation.
Yet these powers did not belong to her and could not be controlled. Her body had also undergone a metamorphosis, after enduring ten years of the cold aura of the Underworld eroding and refining her.
With the Divine Sense and vital energy not matching, naturally, she could not mobilize spiritual energy.
But this was also a characteristic of the Art of Rebirth in the Underworld; because when it was time for soul possession, only the physical body and Spiritual Power were needed. The weaker the Divine Sense, the better, making the process of devouring it all the more effortless.
To solve this problem, aside from Luo Yixuan strengthening her own Divine Sense, the three methods previously mentioned by Elder Ming were also options.