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.
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.
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.
One possible reason could be that in the fanfiction, Hermione has different career aspirations. She might be so focused on her magical research or her work in the Ministry that she feels marriage would hold her back. For example, she could be on the verge of a major discovery in the field of spell - modification and doesn't want any distractions.
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.
Hermione would likely be very angry at first. She is a strong - willed character and being kidnapped would go against all her principles of freedom and rights. She would probably try to reason with Ron immediately, using her logical arguments to make him see how wrong his actions are.
She might be heartbroken. Hermione is a strong - willed character, but being cheated on would surely shatter her. She could initially be in disbelief, given her trust in Ron. Then, she might become angry and start to distance herself from Ron, focusing more on her own studies or other relationships, like her friendship with Sirius.
Another way she could react is by distancing herself completely. She would stop trying to be part of their group and start creating her own identity at Hogwarts. She might explore parts of the castle she's never been to before, find new study nooks, and interact with students she's never really talked to, all while trying to forget about Ron and Harry's cold treatment.
At the beginning, Ron would likely be in shock. He had always thought he and Hermione had a special bond. After the shock, he might become a bit bitter. However, his friends, like Harry, would probably try to cheer him up and help him see that there are other things in life. Eventually, Ron might find a new purpose in his life, whether it's in his magical studies or in exploring new parts of the wizarding world, and try to move on from Hermione.
At first, Harry could be heartbroken. He would wonder what he did wrong to make them leave. He might try to find them and reason with them. However, if he can't reach them, he would likely turn that pain into a driving force. He would focus on his goals, like fighting against Voldemort or protecting the wizarding world, even more fiercely, because he now has to prove himself not only to the world but also to his former friends.
In the fanfiction world regarding Ron leaving Hermione for Lavender, the reactions would vary. Fanfiction writers might take this idea and run with it in different directions. Some might focus on the emotional turmoil Hermione experiences, which could lead to some really angsty and deep stories. Others might explore the relationship between Ron and Lavender, trying to give it more depth and meaning than it had in the original. There could also be those who write fanfictions that are more satirical, making fun of the whole concept while still exploring the possible implications in a light - hearted way.