One possible reason could be competition. Maybe in this fanfic, they are competing for something like recognition in the ninja world. Naruto, as a female, might feel that Sasuke is getting more attention or opportunities, which makes her jealous and eventually turns into hatred.
One possibility for such a fanfic is that Naruto has been through some kind of trauma that makes him view Sasuke and Sakura differently. For example, if Naruto was betrayed by someone he trusted deeply who had similarities to Sasuke and Sakura in some aspects. It could change his perception of them completely and fuel his hatred in the fanfic.
In such a fanfic, one possible reason could be Naruto's feeling of being left out. Maybe he sees Sakura's constant focus on Sasuke and feels neglected in their friendship triangle. Another reason might be jealousy. If Naruto has unrequited feelings for Sakura, seeing her love for Sasuke could turn to hatred over time.
The relationship would become very tense. Naruto would likely avoid Sakura and Sasuke. There would be no more of the friendly banter or the complex emotional triangle that was there before. It's a complete shift from their normal relationships in the original story.
The change is significant. In the original, they had a bond that was slowly developing. But here, Naruto's hatred means that any positive interactions they had are now replaced with hostility. For example, in the original, Naruto would always try to bring Sasuke back when he left. But in the fanfic, she might be more inclined to stop him by force or even wish him harm.
One reason could be a misinterpretation of their complex relationship. In the original story, Naruto actually cares deeply for Sasuke. But in fanfiction, the author might be exploring a 'what if' scenario where Naruto's frustration turns to hate due to Sasuke's repeated betrayals. Another reason could be to create a more angsty or dramatic plot. By having Naruto hate Sasuke, it can introduce new conflicts and character developments that are different from the canon.
The original story focuses on Naruto and Sasuke's relationship as well as Sakura's love for Sasuke as a driving force for her growth. But the fanfic where Sakura hates Sasuke takes a different turn, it might focus on different aspects of Sakura's character, like her independence and self - realization without the influence of her love for Sasuke.
Another reason might be related to their different ideologies within the ANBU. Naruto may have believed in a more collaborative and friendly approach within the organization, while Sasuke might have been more focused on individual achievement and power. This fundamental difference could lead to Naruto hating Sasuke in the fanfiction.
Maybe in the fanfic, Sasuke has done something to betray Sakura's trust. For example, he might have left the village again without considering her feelings.
I'm not sure specifically which 'fem Sasuke hates Naruto' fanfiction to recommend. There are so many fanfictions out there. You could try searching on popular fanfiction websites like Archive of Our Own or FanFiction.net and use those keywords to filter the results.