Yen first impression i had? Run,Geralt,Run!!!....My point exactly, when new players meet Yen the immediate impression is, he look for her? She hot but her attitude sucks. When they meet Triss it's like bubbly feeling all the time.
During the game you can see the flame in Geralt and Triss relationship reignite. You can see their hesitations, hurt and confusion. None want to say something they I'll regret. Slowly Geralt and Triss love for each other spills over on the Docks of Novagrad.
She promise to be by his side but for some reason the Dev felt it wasn't necessary to keep that promise. By his side mean by his side.