Drabble 6:

Hermione was looking through a book in the library. After her fight with Ron, she realised she didn't know any of the rules in the Wizarding World about relationships.

"... The legal age... Age differences... pregnancy... same sex relationships... AHA! Student teacher relationships; page 490."

There are no ruled against Student Teacher relationships. As long as they are both consensual and they follow the other relationship laws, Students and Teachers are allowed to date.

Hermione couldn't believe what she was reading. She could date Professor Snape...

Hermione's mood perked up. And for the rest of the day, she planned. Planned to win Snape over.