Another scenario could be that Snape makes a deal with Bellatrix. He offers her something she wants in exchange for leaving Hermione alone. This could be information, a powerful magical item, or even a promise of his own loyalty in a different matter. However, this would be a very complex and risky move on Snape's part in the context of the fanfiction world.
In some fanfictions, Snape anticipates Bellatrix's move against Hermione. He might have been spying on Bellatrix and discovers her plan. So, he gets to the location where Bellatrix is about to attack Hermione early and sets up a counter - measure. It could be a magical barrier or a spell that nullifies Bellatrix's attack.
One possible scenario is that Snape steps in during a confrontation. Bellatrix is about to harm Hermione, and Snape, using his quick reflexes and advanced magic, stops her. He could be acting out of his own sense of right and wrong, or perhaps because he has a hidden agenda that involves keeping Hermione safe.
Perhaps in the fanfiction, Bellatrix stabs Hermione as a way to get to Harry Potter. She might think that by harming Hermione, she can draw Harry out and into a trap. Hermione is one of Harry's closest friends, so this would be a strategic move on Bellatrix's part.
One possible scenario could be that Ron says something really mean to Hermione during an argument, and Draco, who has secretly been observing Hermione's intelligence and kindness, steps in to defend her. Maybe he uses his quick wit to shut Ron down verbally.
In a fanfiction, Snape might be hard on Hermione during detention. He could assign her extremely difficult tasks that are almost impossible to complete within the given time, just to test her limits. For example, making her organize his entire store of potion ingredients in a very specific and difficult - to - achieve order.
One possible reason could be that Snape sees Hermione's value as a brilliant student. He might recognize her potential and not want it to be wasted just because of her dad's actions or situation. Maybe he has a sense of justice deep down, despite his often cold exterior.
He could use his position of authority. Snape might confront the abuser directly. Since he's a teacher, he has the power to intimidate and put a stop to any immediate harm. He could also give Hermione a safe place to stay, like his own quarters (if it's within the rules of the fanfiction world).
In this kind of fanfic, one possible scenario could be that Harry uses his quick thinking and magical skills. For example, he might use a stunning spell on the troll just in time to stop it from harming Hermione. Another scenario could be that Harry lures the troll away from Hermione, using his knowledge of the troll's behavior. Maybe he throws something noisy in the opposite direction to draw the troll's attention.
One possible scenario could be that Hermione confronts Snape about his unfair treatment of Gryffindor students. Maybe she has evidence of him being overly harsh and she stands up to him in a classroom setting.
One scenario could be that Draco witnesses Hermione being bullied by some Death Eater - sympathizing students. He steps in and uses his quick wit and knowledge of magic to outsmart them. Another could be in a situation where Hermione is being wrongly accused of a crime and is facing abuse in the form of unjust imprisonment. Draco, having some influence in the Ministry due to his family, intervenes and clears her name.
Well, one possible scenario could be that in the fanfiction world, there are dark wizards or forces targeting Hermione for her knowledge or power. Snape, with his skills and knowledge of the dark arts, could use his magic to shield her from attacks. For example, he could set up protective spells around her when she is studying in the library or traveling around Hogwarts.
One possible scenario could be a moment of intense conversation where Hermione is sitting in Snape's lap and they are having a deep discussion about magic theory that only they understand. It might be a turning point in their relationship in the fanfiction world.