Comment by Abiss on To My Husband’s Mistress - Chapter 48

She's a fake. You know how she's been searching for "her sister"? She IS that sister.
The real Lianca is hiding, that's why this bi*** is trying to find her. 

She's an illegitimate child. When she meet Lianca she summoned a demon and he gave her 3 wishes in exchange of death and destruction.

1 wish... she wanted to be Lianca. The price was to burn down her house and kill her family. When she cries that she lost her family... it's because she killed them. 

2 wish... she wanted Asther to fall in love with her forever. The price was to kill his wife. But because she failed to kill the FL, Ashter's love is temporary and he will stop loving her soon.

She doesn't know the FL survive, so she doesn't know her wish was never granted. 
And the demon hates her, that's why he hasn't told her that the FL survived and who she is.
He wants her dead, but since they have a contract, he can't harm her.... but he can let the FL harm her as much as she wants.  And he will.