Severus Snape himself is a very powerful wizard. He might be able to defend himself without much external help at first. However, if the situation escalated, some of his Slytherin students who respected him might come to his side. They could try to create a distraction or use some basic spells to help him until more powerful wizards like Dumbledore or McGonagall arrived.
Professor McGonagall could also be a likely candidate. She was a fair and just teacher. Even though she might be surprised by Hermione's actions, she would not let Snape be unjustly harmed. She might use her Transfiguration skills to separate Hermione from Snape if the situation was dangerous.
Dumbledore might come to Snape's aid. Dumbledore always had a somewhat complex relationship with Snape, and he would likely step in to prevent things from getting too out of hand. He could use his powerful magic to stop Hermione and then try to sort out the situation calmly.
One possible reason could be a misunderstanding. Maybe Hermione thought Snape was involved in some dark plot against her friends. In the wizarding world, there are often secrets and deceptions, and if she got some false information, it could lead her to take such drastic action.
It's hard to say who would be the clear winner. Hermione is intelligent and quick - witted, but Snape has years of experience and a great deal of magical knowledge. If it's a battle of words, Hermione might hold her own for a while, but Snape could use his authority to shut her down.
It could be rival students from Hogwarts who are jealous of their magical abilities. There are always some students who might be envious and could turn to the dark side of magic to try and harm them.
Well, in some fanfictions, Snape might use his advanced potions knowledge. He could brew a special healing potion for Hermione. Maybe it's a modified version of a known potion, like the Essence of Murtlap that has strong healing properties.
Harry Potter could visit Snape in the hospital. Despite their past differences, Harry might feel a sense of obligation or curiosity. He could be there to finally have an honest conversation with Snape and perhaps gain a better understanding of his actions throughout the years.
Snape might be suspicious at first. He might think it's some sort of trick or part of a bigger plot. However, as he observes Hermione more closely and realizes the genuineness of her situation, his attitude could gradually change to one of reluctant assistance. He might even offer some words of wisdom, albeit in his typical sarcastic way, to help Hermione regain her strength.
She might be required to research in the restricted section of the library. Given her penchant for knowledge and Snape's often - dark and esoteric interests, the restricted section could hold the key to whatever he needs help with.
In fanfiction, Snape might be drawn to Hermione because of her intelligence. She's extremely bright and her thirst for knowledge could be appealing to Snape, who also values intelligence highly. Her ability to think quickly and solve problems might catch his attention.
One possible secret could be about his past relationship with Lily Potter. Maybe he reveals how much Lily meant to him and the complex feelings he had towards her, which in turn influenced his actions throughout the series. Another secret could be related to certain spells or potions that he has discovered but kept hidden from others in the wizarding world.
One challenge could be his own reputation. Snape has a rather dark and brooding image at Hogwarts. So, other students or even some teachers might be suspicious of his motives for being Hermione's guardian. Also, Hermione is very independent - minded, which might clash with Snape's over - protective tendencies at times.