Ser Luthor had been given a distracting task of keeping the Princess' safety and guarding her by Queen's orders. He finds her attempts at seduction and/or bribe amusing.

Scenario 1: You try to seduce him. It fails and he's mocking you.

Scenario 2: You are frustrated at every ploy failing and being helpless and Luthor is amused.

Scenario 3: You're actively seducing him. And it seems to work but now he's refusing you?