Force
It could have been second year: Millicent breathing heavily; Hermione tangled, trapped in her grasp; both women unwilling to surrender.
It wasn't.
They broke apart, wary. Millicent destroyed the lock with a barrage of red light; the door creaked open. Hermione pocketed the proffered wand – her own – and fled. The empty, echoing corridors Millicent suggested led her to freedom.
Days later, secure in her apartment, Hermione touched her lips slowly, shuddered and remembered. She scowled at the half finished report on her desk, and finally inked: 'Millicent Goyle seems unsatisfied with her lifestyle, and willing to defy Voldemort if necessary.'