This is an interesting topic. It all begins in "The Bounds of Reason". That was the first story, already heavy on destiny.
Afterwards all the Ciri chapter(s) and "Something More". We can just look at the title of the book -
The Sword of Destiny.
"Excuse my boldness and my frankness, Yennefer.
It's written on your faces, I don't even need to read your thoughts.
You were made for each other, you and the witcher. But nothing will come of it. Nothing. I'm sorry."
"I know." Yennefer turned a little pale. "I know, Villentretenmerth. But I too would like to believe
that there is no limit as to what's possible or at least that this limit is very distant."
Sapkowski is a destiny maniac, however it was never explicitly confirmed, nor denied.
'We were made for each other,' she murmured.
'Perhaps even destined for each other. But none of this can happen.
It's a shame. We will have to separate when the day breaks. It can't be otherwise.
We have to separate so as not to hurt each other. Destined for each other, made for each other,
but the one who created us should have thought of something more. Forgive me. I had to tell you.'
We could speculate a lot of course. Which is what makes Andrzej Sapkowski such an outstanding author. Just like Ciri was destined for Geralt - which was however deeply explored and explained - Yennefer and Geralt could be destined for each other as well and we could phrase it as "made" for each other and that was mentioned multiple times in the books. So yeah, perhaps there really was some "higher" bound. They were destined to what... meet each other? So that Geralt could fulfill his destiny and find Ciri, which would (did) eventually lead to Yennefer fulfilling her purpose - very much like Villentretenmerth himself? Were Ciri and Yen "destined" too? Belleteyn? Through Geralt? Are all three of them destined
for each other? Yeah, Sapkowski's books are filled with that shit and trust me, the more you think about it, the crazier it (you) becomes. It drives me insane sometimes (all the time). "Fighting" with the golden dragon symbolizes the fight with destiny itself in the witcher universe. And so does her whole relationship with Geralt. Yennefer knows she's condemned
to death and cannot fulfill her purpose as a woman, such is her burden and the price she had to pay (willingly or not) for becoming a sorceress. But she refuses to reconcile with such a fate, she doesn't accept that she's doomed and cannot procreate, she tries to fight the limits of possiblity - within or beyond the bounds of reason. Should it be the Djinn fiasco
in Rinde, or the delusional "kill the dragon for me please Geralt". That's where the "fight with destiny" analogy comes in.
"And the goal at the end of the path?"
"Here it is." Villentretenmerth raised his forearm, frightened, the young dragon started to chirp.
"Here is my goal, my purpose. Thanks to him, I shall prove, Geralt of Rivia, that there is
no limit as to what's possible. You too, one day, will discover such a purpose, witcher.
Even those who are different deserve to live. Goodbye, Geralt. Goodbye, Yennefer."
It was similar for Geralt too. Not entirely, or well - to make my thoughts clear - it wasn't the driving factor of his character. But it was there, and it grew stronger with time... Geralt knew that he was doomed to be a witcher and a killer for the rest
of his days. He kept moving, but deep inside he hated his "fate". I noticed this in the very beginning, when I was reading some chapters from The Last Wish short story collection for the first time... It made his character very interesting for me, he was leading that typical fight with himself and was trying to find the purpose. This part from "Something More" nails it:
'Belleteyn!' she cried suddenly. Geralt felt the shoulders pressed against his chest rise and fall.
'They have fun. They celebrate the eternal cycle of nature. And us? What do we do?
We, the relics, those condemned to death, to extermination and oblivion.
Nature is reborn, the cycle repeats itself. But not us, Geralt. We can't perpetuate ourselves.
We are denied that possibility. We have inherited the gift to do extraordinary things with nature,
sometimes against it, but we have been deprived of what is most simple and natural in return.
What does it matter that we live longer than humans? There is no spring after the winter.
We are not reborn, our end carries us with it. But something draws us to the fires,
even though our presence is a cruel joke, a sacrilege against this festival.'
She fell silent. He didn't like to see her fall into such darkness.
He knew the reason too well. It's starting to gnaw at her again, he thought.
There had been a time when it seemed that she had forgotten or accepted her fate.
He moved his shoulders, rocking her like a child. She didn't resist.
Geralt wasn't surprised. He knew that she needed it.
So yeah, just some food for thought. I better stop before I get too deep, I already wrote a bit too much. It was mentioned in the books several times and it still remains an unanswered question. I mean there is a whole book dedicated to it, and even that isn't enough. Imagine all the passages we could dig up and discuss. I believe destiny might have played a part.
But then again...