She was surely casting some sort of magic on him. All he wanted was to pay his tab and run far away from his pub - away from her. Hermione Granger was trying to get to know him and he felt like he was completely off the market for that. He had no energy to give, no charisma to show, no personality to indulge in. He was a shell at this point of his life and Granger had no business trying to know even a sliver of what Draco used to be. 