Often, the plot starts with Hermione showing signs of depression, like isolation or a drop in academic performance. Then Snape notices. He may be initially reluctant to get involved but his sense of duty as a teacher or some hidden softness makes him step in.
One popular fanfiction in this theme might be 'A Helping Hand'. In it, Snape initially approaches Hermione with his usual gruffness but gradually reveals his intention to help her out of her depression. Another could be 'Finding Light' where Snape uses his knowledge of potions and magic to try and lift Hermione's spirits.
One great fanfiction in this category could be 'The Unlikely Bond'. In it, Hermione stumbles upon Snape's hidden past during a library research project. It shows how she begins to see Snape in a different light, not just as the strict professor but as a complex person with a troubled history. It's really interesting to see how their interactions change as she gets to know more about him.
Fanfiction involving such themes can be inappropriate and against the positive spirit of the original 'Harry Potter' series. J.K. Rowling's work focuses on themes like friendship, courage, and magic, not this kind of inappropriate situation. So, I would not recommend seeking such fanfiction.
One common theme is redemption. Often, Snape is portrayed as having a chance at redemption through Hermione's new understanding of him. For example, she might find out about his past love for Lily and how it has shaped his actions, leading her to see him in a more sympathetic light.
It's inappropriate because it involves a rather violent and unethical scenario within the context of the 'Harry Potter' characters. Hermione is a strong, intelligent character, and Snape is a complex teacher figure. This kind of relationship in the form of such an act is not in line with the original characterizations and the overall positive and magical atmosphere of the series.
Well, perhaps Snape uses his position as a teacher to step in. He could have been observing the situation secretly and when Draco was about to do something harmful to Hermione, Snape intervened with a firm command or some magic spell to stop Draco in his tracks.
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).
Well, it could be that Snape has been secretly observing Ron's erratic behavior towards Hermione. When the situation gets out of hand, he intervenes. He might use his position as a teacher to discipline Ron and in the process, saves Hermione. Snape is a complex character with a lot of power and knowledge, so he could use various means like his occlumency skills to sense the danger Hermione is in and act accordingly.