Hermione would probably be deeply hurt at first. She trusts Harry and Ron so much, and being abandoned by them would be a huge blow. But she's also very determined. So, she might throw herself into her studies even more, using her knowledge as a way to cope and also to find a solution to the situation.
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.
It could be that Ron and Hermione abandon Harry due to a prophecy that they misinterpret. They believe that by being with Harry, they will bring doom to the wizarding world. So they go into hiding. Harry, on the other hand, is determined to change the course of the prophecy. He embarks on a journey to find the truth behind it, all while feeling the pain of his friends' desertion. He has to fight against dark forces that are taking advantage of the situation.
In such a fanfiction, it might be that Harry and Ron are influenced by a powerful dark spell. This spell makes them see Hermione as a threat, so they abandon her. Hermione then has to find a way to break the spell's influence on them while also dealing with the loneliness and danger she's now in. She could seek help from other Hogwarts students or even some friendly magical creatures.
It could also be that Hermione, after being abandoned, decides to leave Hogwarts for a while. She travels to different magical places, perhaps some ancient wizarding libraries or hidden magical communities. There, she meets Draco Malfoy who is also on some sort of self - discovery journey. At first, they are both hesitant around each other, but as they share their experiences and knowledge, they start to form a bond.
Hermione may also become more empathetic towards those who are considered outsiders, like Draco. Having been abandoned by her closest friends, she can understand what it's like to be alone. This could lead to her reaching out to Draco in a way she might not have before. She could see past his Slytherin exterior and try to understand his insecurities and motives, which in turn could change her own character as she becomes more open - minded.
Well, it might also lead to a split in the wizarding community. Some might side with Ron and Hermione, believing they had a good reason to abandon Harry. Others would be outraged and try to find Harry and bring him back. This could create chaos and internal conflict within the wizarding world, making it vulnerable to outside threats as well.
In fanfiction, their friendship often develops through shared challenges. For example, when they face a new dark magic threat in the wizarding world, they rely on each other more. Harry's leadership, Ron's humor in tough situations, and Hermione's knowledge combine to make them closer. They also develop their friendship by having deep conversations about their fears and hopes for the future. Maybe Harry shares his concerns about being the Chosen One, and Ron and Hermione support him wholeheartedly.
Yes, there are many great Harry Ron Hermione fanfictions out there. You can find them on various fanfiction websites. Some focus on their adventures during the Hogwarts years that were not fully explored in the original books, like a story where they go on a secret quest in the Forbidden Forest.