She was the first of the Rats to take an (almost over-abundant) interest in Ciri, who was being held captive along with Kayleigh. Later that night, Mistle chastised Kayleigh for attempting to rape Ciri (who was too emotionally drained, due to her recent past experiences, to resist). Once Kayleigh was gone, Mistle took advantage of the now half-dressed Ciri. Mistle attempts to build more on the purely-physical relationship, but Ciri remains emotionally distant and even admits she's only in it because she doesn't want to be alone again.
Before leaving the Rats for good, Ciri gets the same tattoo (a rose) as Mistle on her inner thigh. After a night of physical relations Mistle catches Ciri the next morning attempting to leave. She does not stop her, but concludes that Ciri had been more receptive because she was going to leave and that once Ciri left she would forget her. Ciri promised to never forget her and that she would come back for her "in a six-horse gilded coach. With a retinue of courtiers" and change her fate as well as show her how much she is able to change. Before she finally leaves, the two kiss and tell each other "I love you."
When Ciri heard of Bonhart's plans to kill the Rats, she returns to the village in an attempt to save them. Unfortunately she was too late and arrived only in time to watch Mistle die by Bonhart's blade, earning Ciri's ire in the process which would eventually prove lethal to him.