Zhong Niangyao wasn't foolish, so she naturally could see that Meng Rou wasn't truly repentant. She was simply willing to temporarily bow her head to save her own life.
However, that didn't concern her. The one she actually came to save today wasn't Meng Rou but the infant ghost.
That infant ghost really was pitiable. It finally had the opportunity to be reincarnated as a human but had its hopes shattered again due to Meng Rou's actions. Even more so, due to its resentment, it had already transformed into an Evil Ghost.
If in the end, the infant ghost really did kill Meng Rou and became stained with blood, then wanting to be reincarnated as a human again wouldn't be easy. Moreover, upon returning to hell, it would still be punished.
For the sake of a Meng Rou, it wasn't worth it.