hismastersvoice: Yeah, problem is, as far as I remember, Yennefer and Triss had plenty of time to discuss any and all of the possible "misunderstandings" they might have had before the final scenes in Rivia and I can't recall any hostility between the two.
Not to mention if I had to choose between a manipulative, cold, cheating bitch and an equally manipulative bitch that seem to care for me, I'd pick the later.
callofstalker: Which one is which(only read the english translated ones)?
Yennefer is the more typical sorceress. In many ways, she is a lot like Philippa and Sile, but she was never quite as interested in politics as they were. Definitely out for number one, so to speak. Geralt's wish that tied her to him surprised and touched her, and she really loves him for it, but it didn't stop her from having a turbulent relationship with him and affairs with other people. She has very limited loyalties--Geralt and Ciri, and Ciri is the priority.
Triss is genuinely friendlier and more idealistic, but she's terribly insecure and can be manipulated by domineering people. It tends to get her into trouble because her loyalties get divided. I don't really agree that she betrayed Yennefer (even with Geralt, she's wrong but there are circumstances that complicate the situation), but she certainly "let her down". At the moment of real crisis at the end of the fifth book, however, Triss chooses Geralt, Ciri, and Yennefer over everything else. It's just that it takes a crisis for her to find the strength to do it.