Even, it might not be long before she gets completely pushed out of this body.
But what confuses Shen Jingxian is that she has been in this body since birth. Rather than saying she's crossed over, it's more accurate to say she's reincarnated. She reincarnated into this world, becoming a princess, while carrying memories from her past life.
Princess Yi Fen is her, Shen Jingxian is her, she belongs to this world, this is her body.
Since this body originally belongs to her, there isn't such a thing as an original soul still existing.
Moreover, from the words of the Hidden Guard earlier, Shen Jingxian could surmise that what the Princess inside her body knows is the world from the book, not the world she's living in now.
After all, in her world, Wen Ranchen never treated her badly, even made a promise with her.
But the Princess who suddenly appeared in her body doesn't know this.
From her clamoring to marry Wen Ranchen, it's already evident that she doesn't know her own memories.
