Before he could respond, the door slammed open. Umbridge stood in the doorway, smiling at the both of them. She stepped inside.
"What do we have here?" Umbridge asked. "Two students in a classroom, unsupervised."
"Hello, Professor Umbridge," Hermione said. "We were practicing some spells."
"I see. That'll be detention for the both of you, then. Tonight, my office."
"What for?" Hermione asked.
"Excuse me?" Umbridge replied at Hermione's question.
"I asked Professor McGonagall where students were allowed to practise spells and she told me that all classrooms were available for the students to use. After all, practising magic is a rather fundamental part of a magical school. Why, if such practice were to become forbidden then the Headmaster might find himself forced to rename the school to Hogwarts School of Muggle Subjects."
Harry kept his face blank while Hermione lectured Umbridge like a five-year-old.
"I – you –" Umbridge stuttered. "You're not allowed to have these kind of meetings!"
Hermione looked around the classroom. "I'm sorry, Professor Umbridge, but that Decree applies to three or more students. Harry and I are the only ones here, not counting yourself ... and – no offence meant – but you're not a student."
The furious woman turned and strode out of the classroom.
"Let's add locking and anti-eavesdropping spells to our list," Hermione said.
Harry didn't respond. Instead, he kissed her cheek for pissing Umbridge off in his stead.