The ending of the first season of The Witcher was actually the first time Geralt and Ciri found each other, after looking for each other for what seemed like ages. The showrunner, Lauren S. Hissrich, revealed on Twitter what the final scene was going to look like - and it was even shot that way - but it got cut down because the show didn't include many of the other subplots of the books. In this scene, they even have a semblance of a conversation and not just a quote about destiny.
In a Twitter thread, Hissrich explains the reasoning behind the team cutting out a chunk of the storyline in Brokilon forest– namely (book spoilers) that Geralt and Ciri actually first met there in The Sword of Destiny. But staying so faithful to the source material could have meant a very different season one. Since Ciri spends her time in Brokilon forest during the fourth episode, Hissrich believes that the entirety of Geralt's story would have to have been told before that, in the first three episodes. That would've been too much worldbuilding, even for the most hardcore fantasy fans.
On the other hand, telling Geralt's full stories and still having him meet Ciri in Brokilon forest would have meant not introducing her before season two at the earliest. That may not change much for the people that were fans of the story before the show, but they are not the only target audience. "[If] viewers are investing solely in Geralt for S1, and then get introduced to Yennefer, and several seasons later meet Ciri — it’s potentially confusing to say: forget monster-hunting. Take the last two-three years of what you’ve been watching, and tuck it away. Because that little girl you’ve only just met? SHE is the key to this whole universe, and will be the center of almost every story to come," she explains.
Now, the scene that was shot arguably does not make much sense if the two were meeting for the first time, since they show much more familiarity than they should, and that's why it was edited down to just the quotes about destiny. However, the question of, "Who is Yennefer?" is kept in the final edition, and it probably makes the best possible conclusion to the season. This shows Ciri is a bit more privy to Geralt's thoughts than he might be comfortable with, and hints at the future of their relationship.
Of course, it was expected that any adaptation would have to deviate from the books in some regards. "As writers, we understand that – even when given rationale – fans may not agree with the changes we made. And that's fine! We had to make hard choices, and we didn't get them right every time," the showrunner adds. What's for sure, however, is that the show is trying to tell the story in the best possible way, given its limitations. With the way it started, we're definitely optimistic about the future.