Professor Snape might also be involved. Despite his usual strictness with Hermione, he is a potions master. He could see this as an opportunity to teach her a lesson about being more careful, but also help her because he wouldn't want a student to be in real danger from a botched potion. And there's always the possibility that Dumbledore, with his vast wisdom and knowledge of magic, could offer some cryptic advice that ultimately helps Hermione solve the problem caused by the accident.
Another character who could help is Luna Lovegood. Luna has a unique perspective on magic and often knows about strange and unusual magical creatures and phenomena. She might be able to suggest an ingredient or a method that Hermione hadn't thought of, something that comes from the more esoteric parts of magic that Luna is so familiar with.
One possible plot could be that during a potions class, Draco and Hermione accidentally mix the wrong ingredients. This could lead to a magical reaction that causes them to swap personalities. Hermione might start acting like Draco, being more aloof and sarcastic, while Draco could become more studious and rule - abiding like Hermione. They then have to figure out how to reverse the effect while also dealing with the chaos it causes in Hogwarts.
It could improve their relationship. After the accident, they might realize that they have more in common than they thought. For example, they both are very determined when it comes to potions, just in different ways. This newfound understanding could lead to a grudging respect and the start of a friendship.
In a fanfiction about Hermione's potions accident, perhaps she was trying to create a new potion for a school project. But she misread a step in an old, dusty potions book. As a result, the potion explodes and creates a time - warp effect in the potions classroom. Now Hermione has to deal with different versions of her friends from different time periods all while trying to fix the potion to set things right.
Hermione would most likely be the first to help. She's always been there for Harry and is very knowledgeable in potions. She might quickly assess the situation and try to find a counter - potion or spell to revive him.
One popular one might be 'The Unforeseen Consequences' where the potions accident leads to them having to work together closely to reverse the effects. It has a great plot that delves into their characters.
Often, it creates a situation where they have to rely on each other. For example, in some fanfics, the accident might give them shared magical symptoms that only they can understand and solve together.
Obviously, Hermione herself would be directly affected. But also her friends Harry and Ron. They would be worried about her and would do everything they could to help her. Maybe they would also get into some trouble because of trying to fix the situation. For example, they might break some school rules in their attempt to find a cure for whatever the potion accident caused.
Inuyasha would most likely be the first one to try and help Kagome. He has a strong bond with her and would not stand by while she's in danger. Sango and Miroku would also probably join in the rescue. Sango with her skills in combat using the Hiraikotsu, and Miroku with his spiritual powers. They are Kagome's friends and would feel obligated to help her.
One possible scenario in such a fanfiction could be that during a potions class, Harry and Draco are forced to be partners. They are making a complex potion, and due to their mutual dislike and lack of proper communication, they mess up the ingredients. The potion explodes, covering them both in a strange goo. This accident could be the start of them seeing each other in a different light, perhaps realizing that they are not so different when it comes to making mistakes.
Her parents, of course. They would be an important part of the story as they react to the news. They might be shocked at first but then supportive.