Lavender + Millicent
"What time are you going to bed?" Lavender asked, though immediately gasped and mentally kicked herself. Millicent was a Slytherin and would use any kind of loophole to get out of these questions. The fact that she was allowing three in the first place was amazing and crazy.
"That wasn't one of my questions. They don't count unless I say I'm asking one of my official questions, because otherwise I would never be able to ask a question again. That would be silly." Taking a deep breath, trying to demonstrate some authority rather than appear frazzled and backtracking her way out of this situation.
"So, my first official question is... What's your happiest memory?" You could tell a lot about a person by knowing what made them happy.