She might use her magic in a very direct way. For instance, she could make all of Snape's potion ingredients spill over or cause his wand to fly out of his hand.
Maybe she uses her intelligence to outwit Snape in a very public setting. For example, she could expose some flaw in his teaching methods or a mistake he made in his research in front of the whole class, which would be a form of 'blowing up' at him in an academic way.
Hermione could verbally lash out at Snape with a long tirade. She has a vast vocabulary and a sharp tongue, so she might list all of Snape's wrongdoings in a very public and embarrassing way for him.
It often changes the perception of Snape among other characters. When Hermione stands up for him, some characters who previously disliked or distrusted Snape start to question their own views. For example, in a fanfic, after Hermione's defense, Ron might start to see Snape in a new light and be less hostile towards him.
In this fanfiction, Hermione standing up to Snape might cause a rift in the Hogwarts faculty. Some teachers may side with Hermione, seeing Snape's meanness, while others might defend Snape. This could create chaos in the school and lead to a whole new set of adventures for Hermione and her friends as they navigate this new, more complex situation.
Snape might initially be shocked. He's not one to show much emotion openly, but internally he could be very disturbed. He might start investigating what happened to Hermione immediately, using his skills in potions and magic to try and find a cure or at least understand the cause.
She might initially be shocked and scared. But then she would start to think rationally and try to find a way to outwit Snape. For example, she could start to gather evidence against Snape's own wrongdoings, if there are any, so that she can turn the tables on him.
She might give him cold stares in class. Hermione is not one to shy away from showing her emotions through her expressions. So, every time Snape is in her line of sight, she could fix him with a withering glare that clearly shows her displeasure.
Well, it often starts with a lot of misunderstandings. Snape has his own preconceived notions about Hermione as a Gryffindor student, and Hermione has her own view of Snape as a strict and often unfair teacher. However, as they live together, small moments start to change their relationship. For example, when Hermione is having trouble with a particularly difficult spell, Snape doesn't scold her but instead patiently guides her. This gradually builds trust between them, and they form a unique bond that is different from the typical student - teacher relationship or even a normal father - daughter relationship.
It could initially cause a great deal of shock and discomfort for Hermione. She might view Snape with even more suspicion and dislike, thinking he has some ulterior motive. For Snape, he may be embarrassed by the accidental contact and try to distance himself even more from Hermione, worsening their already strained relationship.
Hermione may also start to scheme. She'll use her intelligence to come up with a plan. For instance, she might start to collect evidence against Snape, something that she could use to counter his blackmail. She'll research old school rules or find out secrets about Snape that she can hold over his head instead.
Well, in some fanfictions, Hermione might use her vast knowledge of magic. She could research rare spells or potions to heal whatever ails Snape. Maybe she discovers a way to reverse the effects of a dark curse that was placed on him. For example, if the curse is sapping his strength, she might find an ancient counter - curse in the library that requires precise incantations and rare ingredients. She would then gather those ingredients, perform the spell, and slowly help Snape regain his health and vitality.
Well, in some versions, Snape might use his magic skills and authority within Hogwarts. He could place protective spells around Hermione or keep a watchful eye on her movements, ensuring Draco can't get close to her without his knowledge.