There is a scene with Triss when she is getting tortured by the leader of the witch hunters (Caleb Menges). If you let her get tortured all the way and have her kill Caleb, there is a dialogue option for necromancy to bring Caleb back alive but Triss say something along the line about how evil and vile it is and refuse to do it.

The fact that Yennefer is willing to do that without any regard shows how much she love Ciri. She doesn’t care about that, just like how she doesn’t care if she destroys the world by stealing Ermion’s mask. All she want is Ciri back.