It was kind of a long development for me. I'd never read the books or played the previous games, but while playing Wild Hunt it had become clear there was something more to Yennefer than what we saw at her introduction. I thought the thing with the magic lobster in the tub was kind of shitty and weird. I didn't like that she shoved Geralt away after kissing him; it made me think that she didn't have much attachment to him, while he was clearly enamored with her. I know it was all a dream that technically didn't ever happen, but I mention it only because I started on more of a negative foot with her than people who read the books first may have.

I decided I needed to do some research on the previous games, not giving the books much thought because I figured there wasn't much relation between the two (silly me). I came to my own conclusions that Triss took advantage of Geralt's amnesia, which was super messed-up to me, so I think that already took her out of the equation when it came to romance for my playthrough. The facts that Geralt and Yennefer had some deep history and that Geralt immediately took off to find Yen after regaining his memory made her even more intriguing to me because there must have been something I wasn't seeing that made her so desirable. I decided to keep an open mind and see where it took me.

Despite all this, I found it really hard not to romance Triss in Novigrad. It was pretty sad staying cold with her, when she was obviously madly in love with G. But I also got a young and naive vibe from her while I got more of an independent lady vibe from Yen, which I already found pretty attractive. I was hoping for payoff in Skellige with Yennefer and I got it through all of those quests onwards. I won't go into gross details, but I got really attached to her (as well as the world and characters as a whole) and decided to read the books simply to get more. I actually found her kind of funny in the first stories, and then she went straight to compelling. I'm on Tower of Swallows now. I don't think it was the djinn's wish that created affection between them at all; in fact, I think it was merely a story tool that made Yen view G much more differently than the passing fancy or useful instrument she'd initially viewed Geralt as. His wish made the way for her actual affection towards him. It all helped things in the game make more sense to me.

Tl;dr: Her depth and development really intrigued me.