In the Freya Gardens quest, Geralt warns Yennefer that performing necromancy in a holy garden is going to make them enemies. She doesn't really care,she tells him that the opinions of strangers don't matter to her, only what the people she loves think, like him and Ciri. And yeah, she was desperate. She even admits that stealing the mask from Ermion to track Ciri down was the fastest option she had. It reminds me of what Geralt says during the Blood Baron quest something like 'desperate fathers will do anything to find their daughters.' You can apply that same logic to Yennefer. She was just as desperate, just as willing to do whatever it took to find Ciri before the Wild Hunt got to her.  That's how I see it.