Hermione would most likely be very touched. Harry is her good friend, and this gift shows that he really understands her. Owls are not only practical but also a symbol of the wizarding world. She would immediately start to name it and make a cozy place for it in the Gryffindor common room. She might also show it off to Ron, with a big smile on her face.
In the fanfic, Harry could have a range of reactions. At first, he might be in denial, thinking that Hermione is just joking or that she will change her mind. Then, when he realizes it's for real, he could get angry, feeling like he's been unfairly judged or rejected. However, over time, he may come to accept it and focus on other aspects of his life, like his fight against the dark forces or his relationships with other friends.
Well, Hermione could start arguing with Harry. She might say that he misread her actions or expressions. She could bring up past events to show that she has no reason to be jealous, like pointing out her own achievements and contributions which should make her above such petty feelings. And she may also question Harry's motives for saying so, wondering if he is trying to manipulate the situation or her emotions for some other reasons.
She might be shocked at first. Hermione is used to being seen as the voice of reason, so being called a hypocrite by Harry could leave her speechless for a moment.
She could get angry. Hermione, being the strong - willed character she is, might feel betrayed that Harry is leaving. She might yell at him, asking him why he's doing this and how he could leave her after all they've been through together. Her anger is really a mask for her deep sadness and fear of losing him.
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.
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.
Harry might be really confused at first. He doesn't understand why Hermione is acting so strange. He might try to talk to her about it, but if Hermione is being stubborn, he could get frustrated. He could also be a bit oblivious and just think Hermione is being overprotective as a friend.
Hermione would likely be defiant at first. She is a brave and strong - willed character. So, she would probably try to resist Narcissa's attempts to intimidate her and would look for ways to escape immediately.
At first, Harry would probably be in shock. He has always considered Hermione one of his closest friends, so her betrayal would be a huge blow. He might not believe it at first and try to reason with her.
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.