Damon certainly couldn't take her back to the apartment since Stefan was there...and his brother definitely didn't need to know what he wanted to do with this Katherine--he didn't need to hear it either. He'd probably got enough of that on Damon's birthday. He could get them a hotel room, but he wasn't exactly sure he had enough on him for that kind of expense, which caused him to frown. Why did everything have to be so complicated? Maybe they could just go back to her apartment, they weren't too far away. "Where would you feel comfortable going?"