The details are slightly different but the result is the same. In the show, Renfri comes out holding Marilka hostage. Geralt tells her to let the girl go then Refri states: "I will kill her. I will kill EVERYONE here until Stregobor comes down." So the threat to the town that the town is unaware of still exists, just in a different way. Considering she was able to hold her own with Geralt fairly well, there's genuine threat there (though she probably can't take the whole town by herself). The ambiguity in the show version isn't whether or not the curse was real but rather whether or not the prophecy was real. Stregobor's story was never strong to begin with but his turning the town against Geralt places him further in doubt. So while they make Renfri more sympathetic (to give more effect to her foreshadowing Geralt's destiny), there's still doubt as to whether or not Geralt made the right choice. Whether Stregobor or Renfri was the greater evil is still in question.
I haven't read the books, so I'm not trying to say the way the show handled it is more or less effective. You and others who read it would know better in that regard. But the ambiguity is still there in the show and it informs Geralt's motivations through the season.
Yeah I read the books and in the books, for me, killing renfri was the obvious choice
In the show it was way more ambiguous which was the right choice which I appreciated.