Fleur had been focusing on the papers she was grading, already being a day behind having put them off for more entertaining times with Gabrielle and Lavender. She was halfway through grading Ginny Weasley's paper, half tempted to just give her a troll grade, she was still a bit bitter about Ginny having sex with her little sister.
And then she felt the hands on her knees, pushing them apart. She gasped and jumped almost out of her seat, ready to hex who - or whatever was touching her before she remembered. She remembered Lavender's plan and instantly relaxed.
Looking up, she noticed that a few students had heard her gasp. "Desole, I zhought I saw a mouse." She quickly explained and the students accepted it and went back to work. She was tempted to look under the desk, but she knew that that could give something away.
So, under the desk, she opened her legs and tried to keep her calm with Lavender's hands on her legs.