Ron might be initially disappointed. He's always had a bit of a crush on Hermione, and this could be a blow to his ego. But if he's true to his character as we know him from the original series, he would respect her decision.
He could also be heartbroken. Ron might withdraw into himself, spending a lot of time alone in his room at the Burrow, not wanting to talk to anyone. He may start to doubt his self - worth, thinking that he wasn't good enough for Hermione.
She might be initially confused. Hermione is a logical person, and without an obvious reason for Harry's silence, she would be at a loss. She would probably try to think back on their recent interactions to figure out what went wrong.
Snape might initially be taken aback. He's not used to students standing up to him so forcefully. He could glare at Hermione with his cold, dark eyes, trying to intimidate her into silence.
Perhaps she tries to find them right away. Using her intelligence and resourcefulness, she starts to search for any clues as to where they might have gone. She could ask other friends, like Neville or Luna, if they have seen Harry and Ron. And she might be determined to bring them back, not willing to give up on their friendship easily.
She might feel heartbroken. In many fanfictions, Hermione has deep feelings for Ron, so seeing him with Lavender could shatter her world. She could initially be in shock and disbelief, and then it might turn into anger or deep sadness as she tries to come to terms with what she saw.
Perhaps Hermione is so overjoyed that she immediately hugs Ron. She might have been secretly hoping for Ron to ask her all along. She then starts talking about what they should wear and how they can make their entrance at the Yule Ball really special.
Ron would probably be shocked at first. He might stutter and not know what to say immediately. Then, a big grin would spread across his face as the news sinks in, and he'd pull Hermione into a tight embrace, telling her how happy he is.
On the other hand, Sasuke could be a bit confused. He might not understand why Naruto, who has been his friend in the past, is refusing to teach him. This confusion could lead to him re - evaluating their relationship and trying to figure out what he has done to deserve this treatment. He may start to question his own actions and motives more deeply.
Harry could be initially confused. He might not understand why Hermione, who has always been there for him, is suddenly pushing him away. So he might try to talk to her to find out the reason.
He might be initially shocked. Snape is used to students being intimidated by him, so Hermione's outburst could catch him off - guard. He may glare at her silently for a moment, trying to regain his composure.