I have a question (got somehow lost with all this information).
Why Yennefer only emerges now, where were she all the time during the events of the 1 and 2 chapters of the game?
Why now?
Did she escape from somewhere?
My memory fails me.
We don't really know as far as the games say. Nilfgaard had her when they grabbed the Kingslayers (she was with them after the Geralt for Yen exchange with the Wild Hunt). Other than that I don't remember Letho saying much.