She realized that Thorin wasn't giving it her all. There was no way to rationalize or deny it, and she didn't know why she'd even bother. It was just the way that Thorin worked. And though she tried to make things work, this she couldn't stand.
"I could end it," she said. "I have no reason to not leave."
She saw Thorin's face pale. If she was going to take her for granted then she at least deserved to be punished for it. Thranduil was old, older than some of the very trees of Mirkwood. She could remember a time before the spiders, before the dragon, back when the world had been so innocent and nice. Thorin could surely remember at least something like that.
Before she had believed that when they were together, when their lips met, the world was slightly better. But Thorin was not perfect, and Thranduil truly wasn't either. They were both queens, and both had their jobs to attend to. Ruling from far away and keeping up a relationship was hard work, especially after their history.
Still, Thranduil tried. She tried, and what did it get her?
She watched Thorin move, saw her open her mouth but no words leave it.
It was time for her to make her decision, and if she had to, Thranduil would drag it out of her. There were other things that she could be doing then watching a dwarf struggle to think of an excuse.