Regardless of the books, if CDPR provides the option for Geralt to have with Triss , not only sexual activity like with many others, but an actual relationship, by choosing him to say that he loves her (and reject Yen), I think they should also provide the correct consequences. If not in form of gameplay (for example quests with Triss or other characters resulting out of the relationship between Geralt and Triss) then just in form of dialog, general presence of Triss or anything that reflects the relationship. I mean that is the whole point of the Witcher GAMES, that you as a player decide what is cannon to the story, every time you PLAY it through. Otherwise why give the option to chose her as a partner at all. Why not just give a usual one night stand option (like with other characters) without the relationship thing. Or even don't give a romance option at all and make them solely friends.
As some others, I also wouldn't "complain" about this if Witcher hadn't such a great narrative, centered around choice and consequences. But it does, and so if this aspect is lacking in some regards, I think it is only a service to the game to point out deficiencies and try to improve them.