And that's completely understandable. Triss, depending on how you look at it, indeed could act rather dishonest or even shady in the games. And while her book introduction was great (how can you not love a girl that almost shits herself to death?), her loyalty to the Lodge really muddles things up towards the end.
While Yen... is quite the character. It's probably safe to say that on everyone who's read the books she left a definite impression - good, bad, maybe mixed, - and that's a sign of a strong character.
I thought her behaviour in the short stories, before Ciri showed up, was rather off-putting, to say the very least. After that, she really has her fantastic moments, even if sometimes her actions may be questionable. If it wasn't for that, I'd probably be on the #TeamYen right about now.