I agree it seems a little shoe-horned to make her a classical witcher. I hope it's not just to give her the title, because she could easily be the protagonist, and/or have the job of being a witcher without the trial of the grasses. She was given the training and education of a witcher, and has magical powers of her own already. Receiving the trials would be a huge deal, narratively, to the characters, and to world building. I could easily see this being a fumbled corporate attempt at placating fans that wanted to see geralt, without any regard for the characters or world building. (Similar to "Rey Skywalker" having absolutely no business being a Skywalker). But that's all speculation. If it's treated as a major plot point, and not done just for the hell of it, it could still be good.