After Snape finds out, the story might take a dark turn. Snape could go on a vendetta against those who wronged Hermione. This could draw him into a dangerous underworld within the wizarding world. Hermione, on the other hand, might start to rely on Snape more and more for protection and support. Their relationship could evolve into an unlikely alliance. And the school as a whole might start to sense the undercurrents of this dark event and the actions Snape is taking because of it.
Once Snape discovers Hermione's situation in the fanfiction, the story development would be complex. Snape would first ensure Hermione's safety. He could assign some of his more trustworthy students to keep an eye on her when he can't be around. In the search for justice, he might have to face some powerful enemies. Hermione would be trying to regain her strength and confidence. Snape could also introduce her to some advanced magic that could help her heal and protect herself. Their interactions would be filled with tension, understanding, and a growing respect as they deal with this harrowing situation together.
The story could develop in many ways. For one, Snape might lead a secret investigation. This could involve him using his Slytherin cunning to uncover the truth behind the rape. As he delves deeper, he might find out there are bigger conspiracies at play. Meanwhile, Hermione would be struggling with the trauma. Snape's actions towards her could gradually change from just a teacher - student relationship to a more protective and empathetic one.