She might be initially confused. After all, Draco is usually her adversary. She could be very suspicious and start to investigate what exactly in the potion is causing this strange phenomenon.
She may be disgusted if she has a strong dislike for Draco. However, if there are some underlying feelings she has been suppressing, she might be a bit flustered. This could lead to her trying to avoid Draco even more to not deal with these new and confusing emotions.
Hermione is a rational person. So, she would probably try to analyze the potion first. She might consult her books or other knowledgeable wizards. Depending on what she finds out, she could either try to reverse the effect if it's negative or dangerous, or she might be forced to work with Draco to understand the full implications of this strange smelling situation if it turns out to be related to something bigger in the wizarding world.
Hermione could become withdrawn. She might isolate herself from her friends for a while, spending her time in the library trying to make sense of it all. She might also feel a sense of betrayal, especially if they had some sort of understanding or relationship developing.
Well, Draco could be very conflicted. On one hand, he has his own pride and his Slytherin upbringing which might tell him to stay away. But if he has developed deeper feelings for Hermione in the fanfic, he might put aside their past differences. He could start by using his family's resources to find a cure or at least better treatments for her cancer. He may also become more protective of her, keeping her away from those who might be unkind about her illness.
It could be a jealous rival. Maybe someone who is envious of Hermione's intelligence or her popularity among her friends. This person might think that by using a love potion on her, they can make her look foolish or get her into trouble.
At first, Hermione would be shocked. But then, she would quickly compose herself. She could play along with Draco and Blaise for a while, pretending to be compliant while she actually gathers information about their motives and the place where they are holding her. She might also try to turn them against each other by highlighting their differences in goals or personalities. Given her intelligence, she would surely come up with a clever plan to get out of the situation.
She might be initially shocked. After all, Draco is usually seen as this tough Slytherin. But then she could feel sympathy. For instance, she might offer him a handkerchief without saying much at first.
She might be heartbroken at first. Hermione is someone who invests deeply in her relationships. She would likely retreat into her studies as a way to cope, burying herself in books to try and forget the pain.
Harry might be really confused at first. He's used to seeing Draco as an adversary, so suddenly having these strong feelings of love would be really disorienting. He might try to fight the feelings or question if they're real. Draco, on the other hand, could either be in denial or embrace it depending on his character in the fanfiction. If he's written as more self - assured, he might go with it at first, but if he's more insecure, he might try to hide it.
Draco might be horrified. He may have his own internal battles as he tries to reconcile the Ron he knew before with the victim of such a terrible act. He could be at a loss for words initially, not knowing how to approach Ron about it.
She would probably be very indignant. Hermione is a rule - follower at heart, and she would feel that she was being unjustly treated. So she would likely try to defend herself immediately, gathering evidence to prove her innocence. For example, if she was accused of cheating on an exam, she would bring out all her study notes and research materials to show that she had studied hard and didn't need to cheat.
In the fanfiction, Draco's shop could have a special love potion. However, it's not the regular love potion but a more refined version that has a milder effect. Also, there could be a potion that helps with sleep, which is much needed for those who have trouble sleeping due to nightmares caused by dark magic.