Serena knew what was running in Leonard's head, and when they were at a certain distance where the others can't hear them, she stopped walking, sighed, before turning to face him.
Leonard also stopped walking as he turned to face Serena. Seeing her look at him as if he was only there to pester her, he felt more aggravated than he already did. "Serena, what are you doing?" he asked frankly, finding no reason to clarify nor pinpoint what he was referring to because he knew that they both already know that.
Serena knew that she should be conscience-stricken, guilty and that she should be thankful for Leonard's concern. However, there was still a stubborn part of her that felt offended. Did he not trust her at all? Did he think that she's just going to… well, she did. But that's not the point.