"Ah," Thalia said, nodding in understanding. "And Damon is..."
Sounded like a boyfriend. Elena had already mentioned a brother, and while a brother got overprotective, it wouldn't be like this - at least in Thalia's experience. She could see Jason being exasperated that she'd be out in a hurricane, but not to the point where she'd be reluctant to tell him. Then again, it wouldn't do to assume.