She might be heartbroken. Ginny could initially be in shock and disbelief. She may retreat into herself, spending a lot of time alone in her room, crying and trying to understand why Harry would refuse.
Ginny could be heartbroken. She might initially be in denial, thinking that Harry will change his mind. She has loved Harry for a long time and expected a future together, so this refusal would be a huge blow to her emotions.
Ginny could be heartbroken. She might have expected to marry Harry after all they've been through together. She could initially go into a state of shock and disbelief, not understanding why Harry has refused.
One possible reason could be that Harry might feel he's not ready for marriage. He has been through so much trauma from fighting Voldemort and might need more time to focus on himself and his own healing. Another reason could be that he might view Ginny more as a sister or a close friend at this point in the fanfiction, rather than a romantic partner.
One possible reason could be that Harry is still haunted by his past traumas and feels he's not in the right mental state to marry anyone. His experiences with Voldemort and the losses he's endured might make him reluctant to bring Ginny into a potentially unstable future.
Maybe Harry has some unresolved issues from his past, like the trauma of losing his parents and many of his friends during the fight against Voldemort. These could make him hesitant to enter into a marriage with Ginny. He might also be worried about how the wizarding world would view their marriage, especially if there are still some who oppose him or his family.
It could be Draco. In some fan fictions, they have a complex relationship that could develop into a romantic interest. Draco's character has a certain allure and his past enmity with Harry could transform into a deep, passionate love in the context of a gay fan fiction.
In some cases, it could be the Ministry of Magic itself. If the Ministry is under the control of corrupt officials, they might force the marriage for their own political gain. They could use Harry's popularity and Ginny's family connections to further their own agendas, and thus become the antagonists that Harry and Ginny have to fight against in the fanfiction.
The original Harry Potter story focuses on Harry's battles against Voldemort and his growth as a wizard. The fanfiction about Harry refusing to marry Snape takes a different turn into the realm of romantic relationships which were not central in the original. Also, in the original, the relationships are more along the lines of friendship, mentorship, and enmity, not romantic love between these two characters.
One possible reason could be that Harry has different feelings towards someone else. Maybe he has developed deep emotional bonds with another male character in the fan fiction and his heart simply doesn't belong to Ginny. Another reason might be that he is still struggling with his own identity and is not ready for a traditional marriage, especially not to Ginny.